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 $69.55   3.246%   $71.8076   $71.81   $71.80   $71.80  
  Purchase #2 $72.72   3.581%   $75.3241   $75.32   $75.30   $75.30  
  Purchase #3 $76.96   10.318%   $84.9007   $84.90   $84.90   $84.90  
  Purchase #4 $76.34   6.734%   $81.4807   $81.48   $81.50   $81.50  
  Purchase #5 $125.31   12.189%   $140.584   $140.58   $140.60   $140.60  
  Purchase #6 $207.30   12.687%   $233.6002   $233.60   $233.60   $233.60  
  Purchase #7 $247.83   7.566%   $266.5808   $266.58   $266.60   $266.60  
  7 purchase totals = $876.01       $954.2781   $954.27   $954.30   $954.30