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	$200.74	3.229%	$207.2219	$207.22	$207.20	$207.20
Purchase #2	$56.36	9.206%	$61.5485	$61.55	$61.55	$61.50
Purchase #3	$90.74	9.840%	$99.6688	$99.67	$99.65	$99.70
Purchase #4	$229.82	11.145%	$255.4334	$255.43	$255.45	$255.40
Purchase #5	$50.26	9.389%	$54.9789	$54.98	$55.00	$55.00
Purchase #6	$10.77	12.420%	$12.1076	$12.11	$12.10	$12.10
Purchase #7	$98.86	13.225%	$111.9342	$111.93	$111.95	$111.90
7 purchase totals =	$737.55		$802.8933	$802.89	$802.90	$802.80