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	$229.43	8.385%	$248.6677	$248.67	$248.65	$248.70
Purchase #2	$35.46	6.544%	$37.7805	$37.78	$37.80	$37.80
Purchase #3	$189.47	13.377%	$214.8154	$214.82	$214.80	$214.80
Purchase #4	$129.30	5.605%	$136.5473	$136.55	$136.55	$136.50
Purchase #5	$53.49	4.838%	$56.0778	$56.08	$56.10	$56.10
Purchase #6	$55.51	10.394%	$61.2797	$61.28	$61.30	$61.30
Purchase #7	$127.58	13.784%	$145.1656	$145.17	$145.15	$145.20
7 purchase totals =	$820.24		$900.3340	$900.35	$900.35	$900.40