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 $158.83   10.761%   $175.9217   $175.92   $175.90   $175.90  
  Purchase #2 $136.42   10.636%   $150.9296   $150.93   $150.95   $150.90  
  Purchase #3 $118.70   5.544%   $125.2807   $125.28   $125.30   $125.30  
  Purchase #4 $212.97   11.711%   $237.9109   $237.91   $237.90   $237.90  
  Purchase #5 $66.97   7.463%   $71.968   $71.97   $71.95   $72.00  
  Purchase #6 $103.75   7.804%   $111.8467   $111.85   $111.85   $111.80  
  Purchase #7 $77.68   8.303%   $84.1298   $84.13   $84.15   $84.10  
  7 purchase totals = $875.32       $957.9874   $957.99   $958.00   $957.90