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 $85.97   11.336%   $95.7156   $95.72   $95.70   $95.70  
  Purchase #2 $104.28   9.246%   $113.9217   $113.92   $113.90   $113.90  
  Purchase #3 $162.63   12.118%   $182.3375   $182.34   $182.35   $182.30  
  Purchase #4 $195.41   12.217%   $219.2832   $219.28   $219.30   $219.30  
  Purchase #5 $214.37   11.435%   $238.8832   $238.88   $238.90   $238.90  
  Purchase #6 $112.98   5.687%   $119.4052   $119.41   $119.40   $119.40  
  Purchase #7 $106.85   10.276%   $117.8299   $117.83   $117.85   $117.80  
  7 purchase totals = $982.49       $1,087.3763   $1,087.38   $1,087.40   $1,087.30