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 $85.31   12.383%   $95.8739   $95.87   $95.85   $95.90  
  Purchase #2 $117.52   6.383%   $125.0213   $125.02   $125.00   $125.00  
  Purchase #3 $171.70   10.827%   $190.29   $190.29   $190.30   $190.30  
  Purchase #4 $240.54   7.263%   $258.0104   $258.01   $258.00   $258.00  
  Purchase #5 $46.71   6.451%   $49.7233   $49.72   $49.70   $49.70  
  Purchase #6 $51.47   7.193%   $55.1722   $55.17   $55.15   $55.20  
  Purchase #7 $96.41   4.749%   $100.9885   $100.99   $101.00   $101.00  
  7 purchase totals = $809.66       $875.0796   $875.07   $875.00   $875.10