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	$225.84	6.824%	$241.2513	$241.25	$241.25	$241.30
Purchase #2	$113.50	13.358%	$128.6613	$128.66	$128.65	$128.70
Purchase #3	$111.42	10.833%	$123.4901	$123.49	$123.50	$123.50
Purchase #4	$155.91	9.571%	$170.8321	$170.83	$170.85	$170.80
Purchase #5	$138.62	10.448%	$153.103	$153.10	$153.10	$153.10
Purchase #6	$154.68	7.329%	$166.0165	$166.02	$166.00	$166.00
Purchase #7	$143.46	5.428%	$151.247	$151.25	$151.25	$151.20
7 purchase totals =	$1,043.43		$1,134.6013	$1,134.60	$1,134.60	$1,134.60