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 $117.53   7.231%   $126.0286   $126.03   $126.05   $126.00  
  Purchase #2 $115.43   9.118%   $125.9549   $125.95   $125.95   $126.00  
  Purchase #3 $90.89   4.275%   $94.7755   $94.78   $94.80   $94.80  
  Purchase #4 $27.48   3.612%   $28.4726   $28.47   $28.45   $28.50  
  Purchase #5 $151.34   11.115%   $168.1614   $168.16   $168.15   $168.20  
  Purchase #6 $178.26   8.358%   $193.159   $193.16   $193.15   $193.20  
  Purchase #7 $237.89   11.722%   $265.7755   $265.78   $265.80   $265.80  
  7 purchase totals = $918.82       $1,002.3275   $1,002.33   $1,002.35   $1,002.50