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 $85.34   8.695%   $92.7603   $92.76   $92.75   $92.80  
  Purchase #2 $149.35   11.383%   $166.3505   $166.35   $166.35   $166.40  
  Purchase #3 $10.84   13.241%   $12.2753   $12.28   $12.30   $12.30  
  Purchase #4 $35.48   6.720%   $37.8643   $37.86   $37.85   $37.90  
  Purchase #5 $184.43   11.274%   $205.2226   $205.22   $205.20   $205.20  
  Purchase #6 $95.86   10.407%   $105.8362   $105.84   $105.85   $105.80  
  Purchase #7 $125.66   5.316%   $132.3401   $132.34   $132.35   $132.30  
  7 purchase totals = $686.96       $752.6493   $752.65   $752.65   $752.70