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 $195.79   6.559%   $208.6319   $208.63   $208.65   $208.60  
  Purchase #2 $114.68   5.450%   $120.9301   $120.93   $120.95   $120.90  
  Purchase #3 $241.73   11.546%   $269.6401   $269.64   $269.65   $269.60  
  Purchase #4 $158.49   10.575%   $175.2503   $175.25   $175.25   $175.30  
  Purchase #5 $132.98   8.289%   $144.0027   $144.00   $144.00   $144.00  
  Purchase #6 $146.54   10.844%   $162.4308   $162.43   $162.45   $162.40  
  Purchase #7 $123.82   8.152%   $133.9138   $133.91   $133.90   $133.90  
  7 purchase totals = $1,114.03       $1,214.7997   $1,214.79   $1,214.85   $1,214.70