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 $59.63   5.528%   $62.9263   $62.93   $62.95   $62.90  
  Purchase #2 $189.76   13.392%   $215.1727   $215.17   $215.15   $215.20  
  Purchase #3 $190.51   11.871%   $213.1254   $213.13   $213.15   $213.10  
  Purchase #4 $116.43   4.240%   $121.3666   $121.37   $121.35   $121.40  
  Purchase #5 $42.67   7.855%   $46.0217   $46.02   $46.00   $46.00  
  Purchase #6 $184.69   12.454%   $207.6913   $207.69   $207.70   $207.70  
  Purchase #7 $16.54   10.104%   $18.2112   $18.21   $18.20   $18.20  
  7 purchase totals = $800.23       $884.5152   $884.52   $884.50   $884.50