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 $38.82   13.698%   $44.1376   $44.14   $44.15   $44.10  
  Purchase #2 $174.98   4.194%   $182.3187   $182.32   $182.30   $182.30  
  Purchase #3 $119.67   10.858%   $132.6638   $132.66   $132.65   $132.70  
  Purchase #4 $230.46   9.561%   $252.4943   $252.49   $252.50   $252.50  
  Purchase #5 $159.69   8.511%   $173.2812   $173.28   $173.30   $173.30  
  Purchase #6 $236.80   8.497%   $256.9209   $256.92   $256.90   $256.90  
  Purchase #7 $177.38   4.749%   $185.8038   $185.80   $185.80   $185.80  
  7 purchase totals = $1,137.80       $1,227.6203   $1,227.61   $1,227.60   $1,227.60