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 $65.48   4.581%   $68.4796   $68.48   $68.50   $68.50  
  Purchase #2 $240.49   13.607%   $273.2135   $273.21   $273.20   $273.20  
  Purchase #3 $151.84   10.804%   $168.2448   $168.24   $168.25   $168.20  
  Purchase #4 $132.97   5.137%   $139.8007   $139.80   $139.80   $139.80  
  Purchase #5 $147.40   4.271%   $153.6955   $153.70   $153.70   $153.70  
  Purchase #6 $131.51   8.294%   $142.4174   $142.42   $142.40   $142.40  
  Purchase #7 $8.64   9.791%   $9.4859   $9.49   $9.50   $9.50  
  7 purchase totals = $878.33       $955.3374   $955.34   $955.35   $955.30