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	$51.89	4.178%	$54.058	$54.06	$54.05	$54.10
Purchase #2	$31.81	6.861%	$33.9925	$33.99	$34.00	$34.00
Purchase #3	$205.50	11.389%	$228.9044	$228.90	$228.90	$228.90
Purchase #4	$43.60	4.518%	$45.5698	$45.57	$45.55	$45.60
Purchase #5	$61.95	13.827%	$70.5158	$70.52	$70.50	$70.50
Purchase #6	$151.73	12.579%	$170.8161	$170.82	$170.80	$170.80
Purchase #7	$177.57	11.680%	$198.3102	$198.31	$198.30	$198.30
7 purchase totals =	$724.05		$802.1668	$802.17	$802.10	$802.20