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 $108.71   5.666%   $114.8695   $114.87   $114.85   $114.90  
  Purchase #2 $58.91   10.865%   $65.3106   $65.31   $65.30   $65.30  
  Purchase #3 $100.72   9.649%   $110.4385   $110.44   $110.45   $110.40  
  Purchase #4 $96.61   7.446%   $103.8036   $103.80   $103.80   $103.80  
  Purchase #5 $204.45   13.763%   $232.5885   $232.59   $232.60   $232.60  
  Purchase #6 $186.62   10.486%   $206.189   $206.19   $206.20   $206.20  
  Purchase #7 $114.25   13.409%   $129.5698   $129.57   $129.55   $129.60  
  7 purchase totals = $870.27       $962.7695   $962.77   $962.75   $962.80