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 $57.76   8.596%   $62.725   $62.73   $62.75   $62.70  
  Purchase #2 $31.88   13.242%   $36.1015   $36.10   $36.10   $36.10  
  Purchase #3 $122.98   4.858%   $128.9544   $128.95   $128.95   $129.00  
  Purchase #4 $203.91   5.570%   $215.2678   $215.27   $215.25   $215.30  
  Purchase #5 $86.90   12.685%   $97.9233   $97.92   $97.90   $97.90  
  Purchase #6 $180.53   8.114%   $195.1782   $195.18   $195.20   $195.20  
  Purchase #7 $249.35   10.456%   $275.422   $275.42   $275.40   $275.40  
  7 purchase totals = $933.31       $1,011.5722   $1,011.57   $1,011.55   $1,011.60