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 $146.59   4.860%   $153.7143   $153.71   $153.70   $153.70  
  Purchase #2 $173.96   11.634%   $194.1985   $194.20   $194.20   $194.20  
  Purchase #3 $56.61   10.130%   $62.3446   $62.34   $62.35   $62.30  
  Purchase #4 $63.50   11.541%   $70.8285   $70.83   $70.85   $70.80  
  Purchase #5 $203.26   4.733%   $212.8803   $212.88   $212.90   $212.90  
  Purchase #6 $101.45   4.133%   $105.6429   $105.64   $105.65   $105.60  
  Purchase #7 $65.35   12.419%   $73.4658   $73.47   $73.45   $73.50  
  7 purchase totals = $810.72       $873.0749   $873.07   $873.10   $873.00