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 $91.76   3.823%   $95.268   $95.27   $95.25   $95.30  
  Purchase #2 $229.49   3.173%   $236.7717   $236.77   $236.75   $236.80  
  Purchase #3 $13.83   13.722%   $15.7278   $15.73   $15.75   $15.70  
  Purchase #4 $41.55   12.873%   $46.8987   $46.90   $46.90   $46.90  
  Purchase #5 $99.92   4.310%   $104.2266   $104.23   $104.25   $104.20  
  Purchase #6 $221.43   10.730%   $245.1894   $245.19   $245.20   $245.20  
  Purchase #7 $233.88   6.612%   $249.3441   $249.34   $249.35   $249.30  
  7 purchase totals = $931.86       $993.4263   $993.43   $993.45   $993.40