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 $107.90   4.663%   $112.9314   $112.93   $112.95   $112.90  
  Purchase #2 $114.36   3.147%   $117.9589   $117.96   $117.95   $118.00  
  Purchase #3 $203.34   6.666%   $216.8946   $216.89   $216.90   $216.90  
  Purchase #4 $194.76   6.475%   $207.3707   $207.37   $207.35   $207.40  
  Purchase #5 $165.47   12.772%   $186.6038   $186.60   $186.60   $186.60  
  Purchase #6 $176.86   8.119%   $191.2193   $191.22   $191.20   $191.20  
  Purchase #7 $249.35   5.216%   $262.3561   $262.36   $262.35   $262.40  
  7 purchase totals = $1,212.04       $1,295.3348   $1,295.33   $1,295.30   $1,295.40