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 $244.86   7.104%   $262.2549   $262.25   $262.25   $262.30  
  Purchase #2 $101.73   4.174%   $105.9762   $105.98   $106.00   $106.00  
  Purchase #3 $136.62   3.487%   $141.3839   $141.38   $141.40   $141.40  
  Purchase #4 $80.34   7.254%   $86.1679   $86.17   $86.15   $86.20  
  Purchase #5 $81.85   12.639%   $92.195   $92.20   $92.20   $92.20  
  Purchase #6 $19.44   3.518%   $20.1239   $20.12   $20.10   $20.10  
  Purchase #7 $157.41   12.778%   $177.5238   $177.52   $177.50   $177.50  
  7 purchase totals = $822.25       $885.6256   $885.62   $885.60   $885.70