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 $68.85   9.498%   $75.3894   $75.39   $75.40   $75.40  
  Purchase #2 $208.80   7.727%   $224.934   $224.93   $224.95   $224.90  
  Purchase #3 $89.73   10.282%   $98.956   $98.96   $98.95   $99.00  
  Purchase #4 $78.31   7.307%   $84.0321   $84.03   $84.05   $84.00  
  Purchase #5 $232.60   4.289%   $242.5762   $242.58   $242.60   $242.60  
  Purchase #6 $47.86   7.750%   $51.5692   $51.57   $51.55   $51.60  
  Purchase #7 $213.61   11.863%   $238.9506   $238.95   $238.95   $239.00  
  7 purchase totals = $939.76       $1,016.4075   $1,016.41   $1,016.45   $1,016.50