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	$73.66	13.621%	$83.6932	$83.69	$83.70	$83.70
Purchase #2	$10.72	10.640%	$11.8606	$11.86	$11.85	$11.90
Purchase #3	$241.93	7.789%	$260.7739	$260.77	$260.75	$260.80
Purchase #4	$48.42	3.540%	$50.1341	$50.13	$50.15	$50.10
Purchase #5	$55.32	10.492%	$61.1242	$61.12	$61.10	$61.10
Purchase #6	$67.78	7.600%	$72.9313	$72.93	$72.95	$72.90
Purchase #7	$71.28	8.736%	$77.507	$77.51	$77.50	$77.50
7 purchase totals =	$569.11		$618.0243	$618.01	$618.00	$618.00