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 $219.27   10.696%   $242.7231   $242.72   $242.70   $242.70  
  Purchase #2 $235.65   11.396%   $262.5047   $262.50   $262.50   $262.50  
  Purchase #3 $79.62   4.160%   $82.9322   $82.93   $82.95   $82.90  
  Purchase #4 $186.35   4.845%   $195.3787   $195.38   $195.40   $195.40  
  Purchase #5 $58.76   6.207%   $62.4072   $62.41   $62.40   $62.40  
  Purchase #6 $152.53   3.742%   $158.2377   $158.24   $158.25   $158.20  
  Purchase #7 $200.42   5.168%   $210.7777   $210.78   $210.80   $210.80  
  7 purchase totals = $1,132.60       $1,214.9613   $1,214.96   $1,215.00   $1,214.90