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	$175.65	5.763%	$185.7727	$185.77	$185.75	$185.80
Purchase #2	$170.31	12.428%	$191.4761	$191.48	$191.50	$191.50
Purchase #3	$95.35	5.379%	$100.4789	$100.48	$100.50	$100.50
Purchase #4	$51.25	5.321%	$53.977	$53.98	$54.00	$54.00
Purchase #5	$99.90	3.718%	$103.6143	$103.61	$103.60	$103.60
Purchase #6	$80.27	13.770%	$91.3232	$91.32	$91.30	$91.30
Purchase #7	$124.58	3.594%	$129.0574	$129.06	$129.05	$129.10
7 purchase totals =	$797.31		$855.6996	$855.70	$855.70	$855.80