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 $93.71   3.464%   $96.9561   $96.96   $96.95   $97.00  
  Purchase #2 $33.85   11.474%   $37.7339   $37.73   $37.75   $37.70  
  Purchase #3 $164.39   11.380%   $183.0976   $183.10   $183.10   $183.10  
  Purchase #4 $164.87   7.331%   $176.9566   $176.96   $176.95   $177.00  
  Purchase #5 $122.36   8.223%   $132.4217   $132.42   $132.40   $132.40  
  Purchase #6 $216.88   6.219%   $230.3678   $230.37   $230.35   $230.40  
  Purchase #7 $100.97   3.849%   $104.8563   $104.86   $104.85   $104.90  
  7 purchase totals = $897.03       $962.3900   $962.40   $962.35   $962.50