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 $227.46   7.698%   $244.9699   $244.97   $244.95   $245.00  
  Purchase #2 $17.60   7.290%   $18.883   $18.88   $18.90   $18.90  
  Purchase #3 $106.82   12.784%   $120.4759   $120.48   $120.50   $120.50  
  Purchase #4 $71.82   6.747%   $76.6657   $76.67   $76.65   $76.70  
  Purchase #5 $222.70   5.359%   $234.6345   $234.63   $234.65   $234.60  
  Purchase #6 $83.77   10.672%   $92.7099   $92.71   $92.70   $92.70  
  Purchase #7 $6.53   5.454%   $6.8861   $6.89   $6.90   $6.90  
  7 purchase totals = $736.70       $795.2250   $795.23   $795.25   $795.30