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	$200.84	5.144%	$211.1712	$211.17	$211.15	$211.20
Purchase #2	$122.65	4.211%	$127.8148	$127.81	$127.80	$127.80
Purchase #3	$80.54	11.548%	$89.8408	$89.84	$89.85	$89.80
Purchase #4	$230.26	9.840%	$252.9176	$252.92	$252.90	$252.90
Purchase #5	$87.91	8.475%	$95.3604	$95.36	$95.35	$95.40
Purchase #6	$19.50	7.141%	$20.8925	$20.89	$20.90	$20.90
Purchase #7	$243.92	11.332%	$271.561	$271.56	$271.55	$271.60
7 purchase totals =	$985.62		$1,069.5583	$1,069.55	$1,069.50	$1,069.60