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 $82.93   13.827%   $94.3967   $94.40   $94.40   $94.40  
  Purchase #2 $32.88   4.788%   $34.4543   $34.45   $34.45   $34.50  
  Purchase #3 $187.53   3.167%   $193.4691   $193.47   $193.45   $193.50  
  Purchase #4 $113.48   5.199%   $119.3798   $119.38   $119.40   $119.40  
  Purchase #5 $206.51   6.761%   $220.4721   $220.47   $220.45   $220.50  
  Purchase #6 $229.77   6.461%   $244.6154   $244.62   $244.60   $244.60  
  Purchase #7 $117.79   7.245%   $126.3239   $126.32   $126.30   $126.30  
  7 purchase totals = $970.89       $1,033.1113   $1,033.11   $1,033.05   $1,033.20