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 $86.76   9.474%   $94.9796   $94.98   $95.00   $95.00  
  Purchase #2 $195.80   5.567%   $206.7002   $206.70   $206.70   $206.70  
  Purchase #3 $19.39   10.863%   $21.4963   $21.50   $21.50   $21.50  
  Purchase #4 $143.57   13.424%   $162.8428   $162.84   $162.85   $162.80  
  Purchase #5 $94.71   5.278%   $99.7088   $99.71   $99.70   $99.70  
  Purchase #6 $122.42   5.637%   $129.3208   $129.32   $129.30   $129.30  
  Purchase #7 $32.83   7.480%   $35.2857   $35.29   $35.30   $35.30  
  7 purchase totals = $695.48       $750.3342   $750.34   $750.35   $750.30