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 $213.75   6.316%   $227.2505   $227.25   $227.25   $227.30  
  Purchase #2 $183.75   6.749%   $196.1513   $196.15   $196.15   $196.20  
  Purchase #3 $45.29   6.789%   $48.3647   $48.36   $48.35   $48.40  
  Purchase #4 $90.47   8.438%   $98.1039   $98.10   $98.10   $98.10  
  Purchase #5 $231.33   12.680%   $260.6626   $260.66   $260.65   $260.70  
  Purchase #6 $168.53   11.197%   $187.4003   $187.40   $187.40   $187.40  
  Purchase #7 $206.39   5.140%   $216.9984   $217.00   $217.00   $217.00  
  7 purchase totals = $1,139.51       $1,234.9317   $1,234.92   $1,234.90   $1,235.10