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	$223.73	3.149%	$230.7753	$230.78	$230.80	$230.80
Purchase #2	$147.49	12.128%	$165.3776	$165.38	$165.40	$165.40
Purchase #3	$132.92	13.816%	$151.2842	$151.28	$151.30	$151.30
Purchase #4	$174.56	9.569%	$191.2636	$191.26	$191.25	$191.30
Purchase #5	$56.25	7.152%	$60.273	$60.27	$60.25	$60.30
Purchase #6	$214.40	5.371%	$225.9154	$225.92	$225.90	$225.90
Purchase #7	$93.55	10.632%	$103.4962	$103.50	$103.50	$103.50
7 purchase totals =	$1,042.90		$1,128.3853	$1,128.39	$1,128.40	$1,128.50