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 $237.87   10.348%   $262.4848   $262.48   $262.50   $262.50  
  Purchase #2 $199.35   8.575%   $216.4443   $216.44   $216.45   $216.40  
  Purchase #3 $162.53   12.351%   $182.6041   $182.60   $182.60   $182.60  
  Purchase #4 $69.36   6.513%   $73.8774   $73.88   $73.90   $73.90  
  Purchase #5 $104.39   13.634%   $118.6225   $118.62   $118.60   $118.60  
  Purchase #6 $117.72   7.668%   $126.7468   $126.75   $126.75   $126.70  
  Purchase #7 $27.39   7.632%   $29.4804   $29.48   $29.50   $29.50  
  7 purchase totals = $918.61       $1,010.2603   $1,010.25   $1,010.30   $1,010.20