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	$116.84	9.395%	$127.8171	$127.82	$127.80	$127.80
Purchase #2	$152.54	5.187%	$160.4522	$160.45	$160.45	$160.50
Purchase #3	$37.35	10.141%	$41.1377	$41.14	$41.15	$41.10
Purchase #4	$214.73	13.659%	$244.06	$244.06	$244.05	$244.10
Purchase #5	$212.50	10.716%	$235.2715	$235.27	$235.25	$235.30
Purchase #6	$196.80	9.226%	$214.9568	$214.96	$214.95	$215.00
Purchase #7	$240.27	4.262%	$250.5103	$250.51	$250.50	$250.50
7 purchase totals =	$1,171.03		$1,274.2056	$1,274.21	$1,274.15	$1,274.30