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 $208.69   13.653%   $237.1824   $237.18   $237.20   $237.20  
  Purchase #2 $204.54   9.681%   $224.3415   $224.34   $224.35   $224.30  
  Purchase #3 $187.47   8.383%   $203.1856   $203.19   $203.20   $203.20  
  Purchase #4 $54.74   12.117%   $61.3728   $61.37   $61.35   $61.40  
  Purchase #5 $33.73   10.451%   $37.2551   $37.26   $37.25   $37.30  
  Purchase #6 $88.89   10.518%   $98.2395   $98.24   $98.25   $98.20  
  Purchase #7 $195.77   7.728%   $210.8991   $210.90   $210.90   $210.90  
  7 purchase totals = $973.83       $1,072.4760   $1,072.48   $1,072.50   $1,072.50