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 $70.62   7.595%   $75.9836   $75.98   $76.00   $76.00  
  Purchase #2 $149.62   5.610%   $158.0137   $158.01   $158.00   $158.00  
  Purchase #3 $197.48   4.214%   $205.8018   $205.80   $205.80   $205.80  
  Purchase #4 $200.84   7.420%   $215.7423   $215.74   $215.75   $215.70  
  Purchase #5 $54.69   9.635%   $59.9594   $59.96   $59.95   $60.00  
  Purchase #6 $24.75   6.351%   $26.3219   $26.32   $26.30   $26.30  
  Purchase #7 $214.97   13.243%   $243.4385   $243.44   $243.45   $243.40  
  7 purchase totals = $912.97       $985.2612   $985.25   $985.25   $985.20