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	$145.84	3.202%	$150.5098	$150.51	$150.50	$150.50
Purchase #2	$246.81	10.338%	$272.3252	$272.33	$272.35	$272.30
Purchase #3	$138.72	5.269%	$146.0292	$146.03	$146.05	$146.00
Purchase #4	$77.52	7.470%	$83.3107	$83.31	$83.30	$83.30
Purchase #5	$159.89	7.841%	$172.427	$172.43	$172.45	$172.40
Purchase #6	$11.31	5.777%	$11.9634	$11.96	$11.95	$12.00
Purchase #7	$230.51	3.378%	$238.2966	$238.30	$238.30	$238.30
7 purchase totals =	$1,010.60		$1,074.8619	$1,074.87	$1,074.90	$1,074.80