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 $43.95   6.606%   $46.8533   $46.85   $46.85   $46.90  
  Purchase #2 $119.38   10.865%   $132.3506   $132.35   $132.35   $132.40  
  Purchase #3 $190.80   5.346%   $201.0002   $201.00   $201.00   $201.00  
  Purchase #4 $110.54   8.550%   $119.9912   $119.99   $120.00   $120.00  
  Purchase #5 $64.60   13.660%   $73.4244   $73.42   $73.40   $73.40  
  Purchase #6 $149.60   5.160%   $157.3194   $157.32   $157.30   $157.30  
  Purchase #7 $8.76   7.581%   $9.4241   $9.42   $9.40   $9.40  
  7 purchase totals = $687.63       $740.3632   $740.35   $740.30   $740.40