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 $62.82   8.210%   $67.9775   $67.98   $68.00   $68.00  
  Purchase #2 $150.84   5.664%   $159.3836   $159.38   $159.40   $159.40  
  Purchase #3 $115.35   9.206%   $125.9691   $125.97   $125.95   $126.00  
  Purchase #4 $67.79   8.248%   $73.3813   $73.38   $73.40   $73.40  
  Purchase #5 $67.64   12.264%   $75.9354   $75.94   $75.95   $75.90  
  Purchase #6 $212.68   5.555%   $224.4944   $224.49   $224.50   $224.50  
  Purchase #7 $68.79   7.802%   $74.157   $74.16   $74.15   $74.20  
  7 purchase totals = $745.91       $801.2983   $801.30   $801.35   $801.40