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 $84.66   11.307%   $94.2325   $94.23   $94.25   $94.20  
  Purchase #2 $167.45   8.515%   $181.7084   $181.71   $181.70   $181.70  
  Purchase #3 $191.70   8.706%   $208.3894   $208.39   $208.40   $208.40  
  Purchase #4 $141.39   8.397%   $153.2625   $153.26   $153.25   $153.30  
  Purchase #5 $66.72   9.763%   $73.2339   $73.23   $73.25   $73.20  
  Purchase #6 $188.57   12.111%   $211.4077   $211.41   $211.40   $211.40  
  Purchase #7 $245.31   10.830%   $271.8771   $271.88   $271.90   $271.90  
  7 purchase totals = $1,085.80       $1,194.1115   $1,194.11   $1,194.15   $1,194.10