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 $59.43   4.816%   $62.2921   $62.29   $62.30   $62.30  
  Purchase #2 $98.90   10.602%   $109.3854   $109.39   $109.40   $109.40  
  Purchase #3 $167.34   8.864%   $182.173   $182.17   $182.15   $182.20  
  Purchase #4 $233.68   5.765%   $247.1517   $247.15   $247.15   $247.20  
  Purchase #5 $169.39   10.170%   $186.617   $186.62   $186.60   $186.60  
  Purchase #6 $59.31   7.507%   $63.7624   $63.76   $63.75   $63.80  
  Purchase #7 $87.60   9.575%   $95.9877   $95.99   $96.00   $96.00  
  7 purchase totals = $875.65       $947.3693   $947.37   $947.35   $947.50