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	$190.35	13.362%	$215.7846	$215.78	$215.80	$215.80
Purchase #2	$12.71	4.518%	$13.2842	$13.28	$13.30	$13.30
Purchase #3	$72.51	6.838%	$77.4682	$77.47	$77.45	$77.50
Purchase #4	$235.66	11.700%	$263.2322	$263.23	$263.25	$263.20
Purchase #5	$180.87	5.125%	$190.1396	$190.14	$190.15	$190.10
Purchase #6	$26.53	7.440%	$28.5038	$28.50	$28.50	$28.50
Purchase #7	$223.38	3.200%	$230.5282	$230.53	$230.55	$230.50
7 purchase totals =	$942.01		$1,018.9408	$1,018.93	$1,019.00	$1,018.90