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 $119.35   5.121%   $125.4619   $125.46   $125.45   $125.50  
  Purchase #2 $94.66   9.368%   $103.5277   $103.53   $103.55   $103.50  
  Purchase #3 $187.64   3.675%   $194.5358   $194.54   $194.55   $194.50  
  Purchase #4 $124.54   3.749%   $129.209   $129.21   $129.20   $129.20  
  Purchase #5 $158.45   4.762%   $165.9954   $166.00   $166.00   $166.00  
  Purchase #6 $8.88   5.367%   $9.3566   $9.36   $9.35   $9.40  
  Purchase #7 $217.35   5.358%   $228.9956   $229.00   $229.00   $229.00  
  7 purchase totals = $910.87       $957.0820   $957.10   $957.10   $957.10