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 $88.40   7.668%   $95.1785   $95.18   $95.20   $95.20  
  Purchase #2 $111.48   12.157%   $125.0326   $125.03   $125.05   $125.00  
  Purchase #3 $109.50   4.460%   $114.3837   $114.38   $114.40   $114.40  
  Purchase #4 $192.89   3.496%   $199.6334   $199.63   $199.65   $199.60  
  Purchase #5 $104.82   4.217%   $109.2403   $109.24   $109.25   $109.20  
  Purchase #6 $35.85   11.635%   $40.0211   $40.02   $40.00   $40.00  
  Purchase #7 $108.67   10.211%   $119.7663   $119.77   $119.75   $119.80  
  7 purchase totals = $751.61       $803.2559   $803.25   $803.30   $803.20