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 $86.42   9.387%   $94.5322   $94.53   $94.55   $94.50  
  Purchase #2 $52.78   12.207%   $59.2229   $59.22   $59.20   $59.20  
  Purchase #3 $81.74   12.831%   $92.2281   $92.23   $92.25   $92.20  
  Purchase #4 $242.29   8.632%   $263.2045   $263.20   $263.20   $263.20  
  Purchase #5 $205.31   6.164%   $217.9653   $217.97   $217.95   $218.00  
  Purchase #6 $166.38   11.515%   $185.5387   $185.54   $185.55   $185.50  
  Purchase #7 $239.32   7.561%   $257.415   $257.42   $257.40   $257.40  
  7 purchase totals = $1,074.24       $1,170.1067   $1,170.11   $1,170.10   $1,170.00