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	$17.53	4.326%	$18.2883	$18.29	$18.30	$18.30
Purchase #2	$207.38	3.548%	$214.7378	$214.74	$214.75	$214.70
Purchase #3	$10.28	4.396%	$10.7319	$10.73	$10.75	$10.70
Purchase #4	$219.63	4.310%	$229.0961	$229.10	$229.10	$229.10
Purchase #5	$145.70	5.346%	$153.4891	$153.49	$153.50	$153.50
Purchase #6	$178.29	10.468%	$196.9534	$196.95	$196.95	$197.00
Purchase #7	$165.89	11.675%	$185.2577	$185.26	$185.25	$185.30
7 purchase totals =	$944.70		$1,008.5543	$1,008.56	$1,008.60	$1,008.60