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 $118.42   7.225%   $126.9758   $126.98   $127.00   $127.00  
  Purchase #2 $93.79   8.350%   $101.6215   $101.62   $101.60   $101.60  
  Purchase #3 $152.42   5.787%   $161.2405   $161.24   $161.25   $161.20  
  Purchase #4 $56.73   12.585%   $63.8695   $63.87   $63.85   $63.90  
  Purchase #5 $151.76   12.217%   $170.3005   $170.30   $170.30   $170.30  
  Purchase #6 $210.55   7.483%   $226.3055   $226.31   $226.30   $226.30  
  Purchase #7 $177.35   7.126%   $189.988   $189.99   $190.00   $190.00  
  7 purchase totals = $961.02       $1,040.3013   $1,040.31   $1,040.30   $1,040.30