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 $55.39   4.591%   $57.933   $57.93   $57.95   $57.90  
  Purchase #2 $214.36   13.872%   $244.096   $244.10   $244.10   $244.10  
  Purchase #3 $68.96   5.811%   $72.9673   $72.97   $72.95   $73.00  
  Purchase #4 $202.38   5.370%   $213.2478   $213.25   $213.25   $213.20  
  Purchase #5 $45.82   12.105%   $51.3665   $51.37   $51.35   $51.40  
  Purchase #6 $71.34   12.352%   $80.1519   $80.15   $80.15   $80.20  
  Purchase #7 $151.56   7.321%   $162.6557   $162.66   $162.65   $162.70  
  7 purchase totals = $809.81       $882.4182   $882.43   $882.40   $882.50