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 $69.67   9.849%   $76.5318   $76.53   $76.55   $76.50  
  Purchase #2 $158.25   10.805%   $175.3489   $175.35   $175.35   $175.30  
  Purchase #3 $133.63   13.317%   $151.4255   $151.43   $151.45   $151.40  
  Purchase #4 $35.91   4.811%   $37.6376   $37.64   $37.65   $37.60  
  Purchase #5 $217.57   12.591%   $244.9642   $244.96   $244.95   $245.00  
  Purchase #6 $107.53   4.310%   $112.1645   $112.16   $112.15   $112.20  
  Purchase #7 $240.79   13.853%   $274.1466   $274.15   $274.15   $274.10  
  7 purchase totals = $963.35       $1,072.2191   $1,072.22   $1,072.25   $1,072.10