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 $82.97   13.761%   $94.3875   $94.39   $94.40   $94.40  
  Purchase #2 $199.50   9.354%   $218.1612   $218.16   $218.15   $218.20  
  Purchase #3 $224.55   9.568%   $246.0349   $246.03   $246.05   $246.00  
  Purchase #4 $198.79   9.439%   $217.5538   $217.55   $217.55   $217.60  
  Purchase #5 $161.74   9.207%   $176.6314   $176.63   $176.65   $176.60  
  Purchase #6 $208.80   13.129%   $236.2134   $236.21   $236.20   $236.20  
  Purchase #7 $72.94   5.448%   $76.9138   $76.91   $76.90   $76.90  
  7 purchase totals = $1,149.29       $1,265.8960   $1,265.88   $1,265.90   $1,265.90