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 $119.34   11.195%   $132.7001   $132.70   $132.70   $132.70  
  Purchase #2 $29.67   11.430%   $33.0613   $33.06   $33.05   $33.10  
  Purchase #3 $62.76   6.201%   $66.6517   $66.65   $66.65   $66.70  
  Purchase #4 $52.35   12.643%   $58.9686   $58.97   $58.95   $59.00  
  Purchase #5 $188.96   8.630%   $205.2672   $205.27   $205.25   $205.30  
  Purchase #6 $83.97   13.461%   $95.2732   $95.27   $95.25   $95.30  
  Purchase #7 $123.46   8.143%   $133.5133   $133.51   $133.50   $133.50  
  7 purchase totals = $660.51       $725.4354   $725.43   $725.35   $725.60