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 $168.28   8.845%   $183.1644   $183.16   $183.15   $183.20  
  Purchase #2 $100.49   11.851%   $112.3991   $112.40   $112.40   $112.40  
  Purchase #3 $183.68   5.205%   $193.2405   $193.24   $193.25   $193.20  
  Purchase #4 $148.38   8.582%   $161.114   $161.11   $161.10   $161.10  
  Purchase #5 $217.63   9.579%   $238.4768   $238.48   $238.50   $238.50  
  Purchase #6 $84.86   8.136%   $91.7642   $91.76   $91.75   $91.80  
  Purchase #7 $198.63   7.809%   $214.141   $214.14   $214.15   $214.10  
  7 purchase totals = $1,101.95       $1,194.3000   $1,194.29   $1,194.30   $1,194.30