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 $168.36   10.687%   $186.3526   $186.35   $186.35   $186.40  
  Purchase #2 $41.88   13.130%   $47.3788   $47.38   $47.40   $47.40  
  Purchase #3 $94.60   12.834%   $106.741   $106.74   $106.75   $106.70  
  Purchase #4 $209.54   5.622%   $221.3203   $221.32   $221.30   $221.30  
  Purchase #5 $90.59   8.551%   $98.3364   $98.34   $98.35   $98.30  
  Purchase #6 $244.32   8.553%   $265.2167   $265.22   $265.20   $265.20  
  Purchase #7 $85.62   3.601%   $88.7032   $88.70   $88.70   $88.70  
  7 purchase totals = $934.91       $1,014.0490   $1,014.05   $1,014.05   $1,014.00