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 $58.72   5.502%   $61.9508   $61.95   $61.95   $62.00  
  Purchase #2 $32.74   12.778%   $36.9235   $36.92   $36.90   $36.90  
  Purchase #3 $206.30   13.372%   $233.8864   $233.89   $233.90   $233.90  
  Purchase #4 $186.53   13.648%   $211.9876   $211.99   $212.00   $212.00  
  Purchase #5 $61.57   12.475%   $69.2509   $69.25   $69.25   $69.30  
  Purchase #6 $215.39   9.464%   $235.7745   $235.77   $235.75   $235.80  
  Purchase #7 $75.48   12.430%   $84.8622   $84.86   $84.85   $84.90  
  7 purchase totals = $836.73       $934.6359   $934.63   $934.60   $934.80