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 $52.66   5.866%   $55.749   $55.75   $55.75   $55.70  
  Purchase #2 $230.35   11.262%   $256.292   $256.29   $256.30   $256.30  
  Purchase #3 $200.65   13.316%   $227.3686   $227.37   $227.35   $227.40  
  Purchase #4 $250.91   5.334%   $264.2935   $264.29   $264.30   $264.30  
  Purchase #5 $75.38   7.523%   $81.0508   $81.05   $81.05   $81.10  
  Purchase #6 $108.30   11.874%   $121.1595   $121.16   $121.15   $121.20  
  Purchase #7 $119.64   5.282%   $125.9594   $125.96   $125.95   $126.00  
  7 purchase totals = $1,037.89       $1,131.8728   $1,131.87   $1,131.85   $1,132.00