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	$79.45	4.107%	$82.713	$82.71	$82.70	$82.70
Purchase #2	$20.72	9.738%	$22.7377	$22.74	$22.75	$22.70
Purchase #3	$95.47	13.213%	$108.0845	$108.08	$108.10	$108.10
Purchase #4	$95.83	13.814%	$109.068	$109.07	$109.05	$109.10
Purchase #5	$214.29	3.205%	$221.158	$221.16	$221.15	$221.20
Purchase #6	$164.62	4.787%	$172.5004	$172.50	$172.50	$172.50
Purchase #7	$125.26	5.829%	$132.5614	$132.56	$132.55	$132.60
7 purchase totals =	$795.64		$848.8230	$848.82	$848.80	$848.90