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 $195.57   8.262%   $211.728   $211.73   $211.75   $211.70  
  Purchase #2 $208.43   10.553%   $230.4256   $230.43   $230.45   $230.40  
  Purchase #3 $216.56   7.489%   $232.7782   $232.78   $232.80   $232.80  
  Purchase #4 $67.65   11.828%   $75.6516   $75.65   $75.65   $75.70  
  Purchase #5 $95.85   4.122%   $99.8009   $99.80   $99.80   $99.80  
  Purchase #6 $48.87   5.307%   $51.4635   $51.46   $51.45   $51.50  
  Purchase #7 $47.88   13.804%   $54.4894   $54.49   $54.50   $54.50  
  7 purchase totals = $880.81       $956.3372   $956.34   $956.40   $956.40