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	$143.46	6.842%	$153.2755	$153.28	$153.30	$153.30
Purchase #2	$87.45	4.202%	$91.1246	$91.12	$91.10	$91.10
Purchase #3	$119.51	6.723%	$127.5447	$127.54	$127.55	$127.50
Purchase #4	$50.42	6.594%	$53.7447	$53.74	$53.75	$53.70
Purchase #5	$28.85	3.754%	$29.933	$29.93	$29.95	$29.90
Purchase #6	$213.71	5.363%	$225.1713	$225.17	$225.15	$225.20
Purchase #7	$229.55	13.499%	$260.537	$260.54	$260.55	$260.50
7 purchase totals =	$872.95		$941.3308	$941.32	$941.35	$941.20