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 $212.57   8.808%   $231.2932   $231.29   $231.30   $231.30  
  Purchase #2 $82.43   13.472%   $93.535   $93.54   $93.55   $93.50  
  Purchase #3 $89.42   9.413%   $97.8371   $97.84   $97.85   $97.80  
  Purchase #4 $125.43   8.466%   $136.0489   $136.05   $136.05   $136.00  
  Purchase #5 $232.86   7.354%   $249.9845   $249.98   $250.00   $250.00  
  Purchase #6 $112.92   11.808%   $126.2536   $126.25   $126.25   $126.30  
  Purchase #7 $119.88   4.361%   $125.108   $125.11   $125.10   $125.10  
  7 purchase totals = $975.51       $1,060.0603   $1,060.06   $1,060.10   $1,060.00