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	$198.59	3.631%	$205.8008	$205.80	$205.80	$205.80
Purchase #2	$149.87	4.621%	$156.7955	$156.80	$156.80	$156.80
Purchase #3	$40.51	5.412%	$42.7024	$42.70	$42.70	$42.70
Purchase #4	$13.72	13.675%	$15.5962	$15.60	$15.60	$15.60
Purchase #5	$220.30	10.525%	$243.4866	$243.49	$243.50	$243.50
Purchase #6	$33.84	12.456%	$38.0551	$38.06	$38.05	$38.10
Purchase #7	$150.35	12.191%	$168.6792	$168.68	$168.70	$168.70
7 purchase totals =	$807.18		$871.1158	$871.13	$871.15	$871.20