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 $43.33   3.331%   $44.7733   $44.77   $44.75   $44.80  
  Purchase #2 $195.86   5.111%   $205.8704   $205.87   $205.85   $205.90  
  Purchase #3 $58.46   3.679%   $60.6107   $60.61   $60.60   $60.60  
  Purchase #4 $112.54   8.673%   $122.3006   $122.30   $122.30   $122.30  
  Purchase #5 $111.82   13.460%   $126.871   $126.87   $126.85   $126.90  
  Purchase #6 $193.34   12.339%   $217.1962   $217.20   $217.20   $217.20  
  Purchase #7 $146.87   12.328%   $164.9761   $164.98   $165.00   $165.00  
  7 purchase totals = $862.22       $942.5983   $942.60   $942.55   $942.70