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	$117.82	8.136%	$127.4058	$127.41	$127.40	$127.40
Purchase #2	$43.72	3.846%	$45.4015	$45.40	$45.40	$45.40
Purchase #3	$242.75	13.662%	$275.9145	$275.91	$275.90	$275.90
Purchase #4	$56.58	13.219%	$64.0593	$64.06	$64.05	$64.10
Purchase #5	$45.37	11.530%	$50.6012	$50.60	$50.60	$50.60
Purchase #6	$224.66	4.684%	$235.1831	$235.18	$235.20	$235.20
Purchase #7	$56.92	6.129%	$60.4086	$60.41	$60.40	$60.40
7 purchase totals =	$787.82		$858.9740	$858.97	$858.95	$859.00