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	$213.87	7.648%	$230.2268	$230.23	$230.25	$230.20
Purchase #2	$233.82	5.817%	$247.4213	$247.42	$247.40	$247.40
Purchase #3	$78.31	9.496%	$85.7463	$85.75	$85.75	$85.70
Purchase #4	$228.84	4.203%	$238.4581	$238.46	$238.45	$238.50
Purchase #5	$53.45	4.386%	$55.7943	$55.79	$55.80	$55.80
Purchase #6	$18.64	12.462%	$20.9629	$20.96	$20.95	$21.00
Purchase #7	$69.30	6.647%	$73.9064	$73.91	$73.90	$73.90
7 purchase totals =	$896.23		$952.5161	$952.52	$952.50	$952.50