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 $40.63   13.243%   $46.0106   $46.01   $46.00   $46.00  
  Purchase #2 $142.66   8.477%   $154.7533   $154.75   $154.75   $154.80  
  Purchase #3 $226.89   11.601%   $253.2115   $253.21   $253.20   $253.20  
  Purchase #4 $185.47   5.127%   $194.979   $194.98   $195.00   $195.00  
  Purchase #5 $151.99   10.228%   $167.5355   $167.54   $167.55   $167.50  
  Purchase #6 $161.96   9.340%   $177.0871   $177.09   $177.10   $177.10  
  Purchase #7 $194.99   11.501%   $217.4158   $217.42   $217.40   $217.40  
  7 purchase totals = $1,104.59       $1,210.9928   $1,211.00   $1,211.00   $1,211.00