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	$125.44	3.802%	$130.2092	$130.21	$130.20	$130.20
Purchase #2	$57.40	7.316%	$61.5994	$61.60	$61.60	$61.60
Purchase #3	$92.79	8.537%	$100.7115	$100.71	$100.70	$100.70
Purchase #4	$214.56	12.668%	$241.7405	$241.74	$241.75	$241.70
Purchase #5	$192.46	6.591%	$205.145	$205.15	$205.15	$205.10
Purchase #6	$228.85	8.191%	$247.5951	$247.60	$247.60	$247.60
Purchase #7	$19.45	4.514%	$20.328	$20.33	$20.35	$20.30
7 purchase totals =	$930.95		$1,007.3287	$1,007.34	$1,007.35	$1,007.20