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	$228.67	4.704%	$239.4266	$239.43	$239.45	$239.40
Purchase #2	$96.48	4.288%	$100.6171	$100.62	$100.60	$100.60
Purchase #3	$165.26	4.403%	$172.5364	$172.54	$172.55	$172.50
Purchase #4	$59.93	10.835%	$66.4234	$66.42	$66.40	$66.40
Purchase #5	$141.78	9.439%	$155.1626	$155.16	$155.15	$155.20
Purchase #6	$122.89	6.150%	$130.4477	$130.45	$130.45	$130.40
Purchase #7	$229.64	10.852%	$254.5605	$254.56	$254.55	$254.60
7 purchase totals =	$1,044.65		$1,119.1743	$1,119.18	$1,119.15	$1,119.10