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 $44.88   4.625%   $46.9557   $46.96   $46.95   $47.00  
  Purchase #2 $95.26   6.247%   $101.2109   $101.21   $101.20   $101.20  
  Purchase #3 $15.98   13.267%   $18.1001   $18.10   $18.10   $18.10  
  Purchase #4 $54.48   13.504%   $61.837   $61.84   $61.85   $61.80  
  Purchase #5 $207.62   11.198%   $230.8693   $230.87   $230.85   $230.90  
  Purchase #6 $82.84   5.175%   $87.127   $87.13   $87.15   $87.10  
  Purchase #7 $64.57   6.236%   $68.5966   $68.60   $68.60   $68.60  
  7 purchase totals = $565.63       $614.6966   $614.71   $614.70   $614.70