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 $119.67   5.596%   $126.3667   $126.37   $126.35   $126.40  
  Purchase #2 $197.90   9.278%   $216.2612   $216.26   $216.25   $216.30  
  Purchase #3 $113.38   9.468%   $124.1148   $124.11   $124.10   $124.10  
  Purchase #4 $226.97   10.132%   $249.9666   $249.97   $249.95   $250.00  
  Purchase #5 $46.39   11.797%   $51.8626   $51.86   $51.85   $51.90  
  Purchase #6 $69.60   8.389%   $75.4387   $75.44   $75.45   $75.40  
  Purchase #7 $28.66   5.217%   $30.1552   $30.16   $30.15   $30.20  
  7 purchase totals = $802.57       $874.1658   $874.17   $874.10   $874.30