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 $211.87   10.133%   $233.3388   $233.34   $233.35   $233.30  
  Purchase #2 $213.88   10.407%   $236.1385   $236.14   $236.15   $236.10  
  Purchase #3 $96.68   6.772%   $103.2272   $103.23   $103.25   $103.20  
  Purchase #4 $173.97   12.643%   $195.965   $195.97   $195.95   $196.00  
  Purchase #5 $197.49   5.256%   $207.8701   $207.87   $207.85   $207.90  
  Purchase #6 $14.40   5.159%   $15.1429   $15.14   $15.15   $15.10  
  Purchase #7 $79.69   3.160%   $82.2082   $82.21   $82.20   $82.20  
  7 purchase totals = $987.98       $1,073.8907   $1,073.90   $1,073.90   $1,073.80