Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $231.95   5.482%   $244.6655   $244.67   $244.65   $244.70  
  Purchase #2 $101.74   12.184%   $114.136   $114.14   $114.15   $114.10  
  Purchase #3 $119.75   11.454%   $133.4662   $133.47   $133.45   $133.50  
  Purchase #4 $80.61   9.419%   $88.2027   $88.20   $88.20   $88.20  
  Purchase #5 $249.38   10.812%   $276.343   $276.34   $276.35   $276.30  
  Purchase #6 $177.51   4.129%   $184.8394   $184.84   $184.85   $184.80  
  Purchase #7 $145.38   10.520%   $160.674   $160.67   $160.65   $160.70  
  7 purchase totals = $1,106.32       $1,202.3268   $1,202.33   $1,202.30   $1,202.30