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 $176.33   12.204%   $197.8493   $197.85   $197.85   $197.80  
  Purchase #2 $51.91   3.115%   $53.527   $53.53   $53.55   $53.50  
  Purchase #3 $129.74   9.807%   $142.4636   $142.46   $142.45   $142.50  
  Purchase #4 $246.55   9.455%   $269.8613   $269.86   $269.85   $269.90  
  Purchase #5 $214.31   9.758%   $235.2224   $235.22   $235.20   $235.20  
  Purchase #6 $168.86   5.603%   $178.3212   $178.32   $178.30   $178.30  
  Purchase #7 $61.35   4.109%   $63.8709   $63.87   $63.85   $63.90  
  7 purchase totals = $1,049.05       $1,141.1157   $1,141.11   $1,141.05   $1,141.10