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	$96.29	7.195%	$103.2181	$103.22	$103.20	$103.20
Purchase #2	$38.70	12.818%	$43.6606	$43.66	$43.65	$43.70
Purchase #3	$144.54	7.833%	$155.8618	$155.86	$155.85	$155.90
Purchase #4	$111.25	6.452%	$118.4279	$118.43	$118.45	$118.40
Purchase #5	$195.54	8.728%	$212.6067	$212.61	$212.60	$212.60
Purchase #6	$113.51	11.467%	$126.5262	$126.53	$126.55	$126.50
Purchase #7	$107.84	8.109%	$116.5847	$116.58	$116.60	$116.60
7 purchase totals =	$807.67		$876.8860	$876.89	$876.90	$876.90