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	$181.39	3.228%	$187.2453	$187.25	$187.25	$187.20
Purchase #2	$230.75	5.869%	$244.2927	$244.29	$244.30	$244.30
Purchase #3	$205.39	7.371%	$220.5293	$220.53	$220.55	$220.50
Purchase #4	$18.74	8.332%	$20.3014	$20.30	$20.30	$20.30
Purchase #5	$54.75	13.766%	$62.2869	$62.29	$62.30	$62.30
Purchase #6	$235.55	9.746%	$258.5067	$258.51	$258.50	$258.50
Purchase #7	$144.32	10.253%	$159.1171	$159.12	$159.10	$159.10
7 purchase totals =	$1,070.89		$1,152.2794	$1,152.29	$1,152.30	$1,152.20