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 $224.86   9.377%   $245.9451   $245.95   $245.95   $245.90  
  Purchase #2 $188.35   13.852%   $214.4402   $214.44   $214.45   $214.40  
  Purchase #3 $68.74   4.706%   $71.9749   $71.97   $71.95   $72.00  
  Purchase #4 $185.26   4.208%   $193.0557   $193.06   $193.05   $193.10  
  Purchase #5 $243.96   10.108%   $268.6195   $268.62   $268.60   $268.60  
  Purchase #6 $223.53   5.815%   $236.5283   $236.53   $236.55   $236.50  
  Purchase #7 $13.41   13.401%   $15.2071   $15.21   $15.20   $15.20  
  7 purchase totals = $1,148.11       $1,245.7708   $1,245.78   $1,245.75   $1,245.70