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 $185.86   5.243%   $195.6046   $195.60   $195.60   $195.60  
  Purchase #2 $244.42   6.465%   $260.2218   $260.22   $260.20   $260.20  
  Purchase #3 $23.64   5.249%   $24.8809   $24.88   $24.90   $24.90  
  Purchase #4 $219.63   13.320%   $248.8847   $248.88   $248.90   $248.90  
  Purchase #5 $234.87   12.139%   $263.3809   $263.38   $263.40   $263.40  
  Purchase #6 $121.82   9.523%   $133.4209   $133.42   $133.40   $133.40  
  Purchase #7 $208.95   4.306%   $217.9474   $217.95   $217.95   $217.90  
  7 purchase totals = $1,239.19       $1,344.3412   $1,344.33   $1,344.35   $1,344.30