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 $182.78   7.604%   $196.6786   $196.68   $196.70   $196.70  
  Purchase #2 $138.56   4.378%   $144.6262   $144.63   $144.65   $144.60  
  Purchase #3 $214.65   10.371%   $236.9114   $236.91   $236.90   $236.90  
  Purchase #4 $27.75   5.215%   $29.1972   $29.20   $29.20   $29.20  
  Purchase #5 $5.83   5.496%   $6.1504   $6.15   $6.15   $6.20  
  Purchase #6 $204.60   6.305%   $217.5   $217.50   $217.50   $217.50  
  Purchase #7 $180.73   7.664%   $194.5811   $194.58   $194.60   $194.60  
  7 purchase totals = $954.90       $1,025.6449   $1,025.65   $1,025.70   $1,025.70