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 $184.40   9.530%   $201.9733   $201.97   $201.95   $202.00  
  Purchase #2 $133.32   8.114%   $144.1376   $144.14   $144.15   $144.10  
  Purchase #3 $140.73   7.167%   $150.8161   $150.82   $150.80   $150.80  
  Purchase #4 $200.96   11.468%   $224.0061   $224.01   $224.00   $224.00  
  Purchase #5 $150.63   10.445%   $166.3633   $166.36   $166.35   $166.40  
  Purchase #6 $244.76   6.791%   $261.3817   $261.38   $261.40   $261.40  
  Purchase #7 $241.32   11.197%   $268.3406   $268.34   $268.35   $268.30  
  7 purchase totals = $1,296.12       $1,417.0187   $1,417.02   $1,417.00   $1,417.00