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 $93.76   4.548%   $98.0242   $98.02   $98.00   $98.00  
  Purchase #2 $39.95   4.114%   $41.5935   $41.59   $41.60   $41.60  
  Purchase #3 $142.91   4.454%   $149.2752   $149.28   $149.30   $149.30  
  Purchase #4 $244.87   4.237%   $255.2451   $255.25   $255.25   $255.20  
  Purchase #5 $112.84   11.653%   $125.9892   $125.99   $126.00   $126.00  
  Purchase #6 $110.78   5.521%   $116.8962   $116.90   $116.90   $116.90  
  Purchase #7 $161.42   8.418%   $175.0083   $175.01   $175.00   $175.00  
  7 purchase totals = $906.53       $962.0317   $962.04   $962.05   $962.00