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	$149.67	5.831%	$158.3973	$158.40	$158.40	$158.40
Purchase #2	$9.78	3.506%	$10.1229	$10.12	$10.10	$10.10
Purchase #3	$105.60	11.218%	$117.4462	$117.45	$117.45	$117.40
Purchase #4	$147.90	3.799%	$153.5187	$153.52	$153.50	$153.50
Purchase #5	$185.54	5.692%	$196.1009	$196.10	$196.10	$196.10
Purchase #6	$164.68	5.603%	$173.907	$173.91	$173.90	$173.90
Purchase #7	$244.61	13.344%	$277.2508	$277.25	$277.25	$277.30
7 purchase totals =	$1,007.78		$1,086.7438	$1,086.75	$1,086.70	$1,086.70