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	$157.26	9.551%	$172.2799	$172.28	$172.30	$172.30
Purchase #2	$165.83	4.343%	$173.032	$173.03	$173.05	$173.00
Purchase #3	$34.34	9.271%	$37.5237	$37.52	$37.50	$37.50
Purchase #4	$95.30	4.238%	$99.3388	$99.34	$99.35	$99.30
Purchase #5	$25.99	4.586%	$27.1819	$27.18	$27.20	$27.20
Purchase #6	$37.38	13.729%	$42.5119	$42.51	$42.50	$42.50
Purchase #7	$9.96	7.202%	$10.6773	$10.68	$10.70	$10.70
7 purchase totals =	$526.06		$562.5455	$562.54	$562.60	$562.50