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	$98.44	10.262%	$108.5419	$108.54	$108.55	$108.50
Purchase #2	$147.58	11.757%	$164.931	$164.93	$164.95	$164.90
Purchase #3	$39.57	9.747%	$43.4269	$43.43	$43.45	$43.40
Purchase #4	$82.47	9.770%	$90.5273	$90.53	$90.55	$90.50
Purchase #5	$249.54	9.630%	$273.5707	$273.57	$273.55	$273.60
Purchase #6	$73.89	3.158%	$76.2234	$76.22	$76.20	$76.20
Purchase #7	$127.87	13.752%	$145.4547	$145.45	$145.45	$145.50
7 purchase totals =	$819.36		$902.6759	$902.67	$902.70	$902.60