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 $88.26   6.788%   $94.2511   $94.25   $94.25   $94.30  
  Purchase #2 $229.56   6.274%   $243.9626   $243.96   $243.95   $244.00  
  Purchase #3 $245.51   5.874%   $259.9313   $259.93   $259.95   $259.90  
  Purchase #4 $175.61   8.295%   $190.1768   $190.18   $190.20   $190.20  
  Purchase #5 $249.69   12.551%   $281.0286   $281.03   $281.05   $281.00  
  Purchase #6 $147.74   7.105%   $158.2369   $158.24   $158.25   $158.20  
  Purchase #7 $248.92   5.643%   $262.9666   $262.97   $262.95   $263.00  
  7 purchase totals = $1,385.29       $1,490.5539   $1,490.56   $1,490.60   $1,490.60