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	$231.84	3.566%	$240.1074	$240.11	$240.10	$240.10
Purchase #2	$62.89	11.816%	$70.3211	$70.32	$70.30	$70.30
Purchase #3	$102.43	9.117%	$111.7685	$111.77	$111.75	$111.80
Purchase #4	$159.75	3.487%	$165.3205	$165.32	$165.30	$165.30
Purchase #5	$208.50	12.611%	$234.7939	$234.79	$234.80	$234.80
Purchase #6	$137.41	7.418%	$147.6031	$147.60	$147.60	$147.60
Purchase #7	$194.52	5.515%	$205.2478	$205.25	$205.25	$205.20
7 purchase totals =	$1,097.34		$1,175.1623	$1,175.16	$1,175.10	$1,175.10