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	$156.90	6.715%	$167.4358	$167.44	$167.45	$167.40
Purchase #2	$44.68	8.434%	$48.4483	$48.45	$48.45	$48.40
Purchase #3	$69.79	3.834%	$72.4657	$72.47	$72.45	$72.50
Purchase #4	$152.62	13.510%	$173.239	$173.24	$173.25	$173.20
Purchase #5	$126.52	8.342%	$137.0743	$137.07	$137.05	$137.10
Purchase #6	$138.37	8.810%	$150.5604	$150.56	$150.55	$150.60
Purchase #7	$184.38	4.106%	$191.9506	$191.95	$191.95	$192.00
7 purchase totals =	$873.26		$941.1741	$941.18	$941.15	$941.20