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 $211.88   6.525%   $225.7052   $225.71   $225.70   $225.70  
  Purchase #2 $108.86   5.301%   $114.6307   $114.63   $114.65   $114.60  
  Purchase #3 $98.42   10.391%   $108.6468   $108.65   $108.65   $108.60  
  Purchase #4 $120.64   9.383%   $131.9597   $131.96   $131.95   $132.00  
  Purchase #5 $107.68   10.749%   $119.2545   $119.25   $119.25   $119.30  
  Purchase #6 $206.91   4.331%   $215.8713   $215.87   $215.85   $215.90  
  Purchase #7 $118.64   10.848%   $131.5101   $131.51   $131.50   $131.50  
  7 purchase totals = $973.03       $1,047.5783   $1,047.58   $1,047.55   $1,047.60