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 $244.81   7.626%   $263.4792   $263.48   $263.50   $263.50  
  Purchase #2 $154.62   9.719%   $169.6475   $169.65   $169.65   $169.60  
  Purchase #3 $200.47   7.732%   $215.9703   $215.97   $215.95   $216.00  
  Purchase #4 $83.97   9.731%   $92.1411   $92.14   $92.15   $92.10  
  Purchase #5 $232.93   5.243%   $245.1425   $245.14   $245.15   $245.10  
  Purchase #6 $64.34   5.707%   $68.0119   $68.01   $68.00   $68.00  
  Purchase #7 $175.29   10.785%   $194.195   $194.20   $194.20   $194.20  
  7 purchase totals = $1,156.43       $1,248.5875   $1,248.59   $1,248.60   $1,248.50