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 $85.93   10.545%   $94.9913   $94.99   $95.00   $95.00  
  Purchase #2 $64.81   3.437%   $67.0375   $67.04   $67.05   $67.00  
  Purchase #3 $116.93   13.300%   $132.4817   $132.48   $132.50   $132.50  
  Purchase #4 $154.45   10.589%   $170.8047   $170.80   $170.80   $170.80  
  Purchase #5 $195.41   3.597%   $202.4389   $202.44   $202.45   $202.40  
  Purchase #6 $92.43   7.378%   $99.2495   $99.25   $99.25   $99.20  
  Purchase #7 $104.32   5.493%   $110.0503   $110.05   $110.05   $110.10  
  7 purchase totals = $814.28       $877.0539   $877.05   $877.10   $877.00