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	$110.95	11.550%	$123.7647	$123.76	$123.75	$123.80
Purchase #2	$146.30	3.557%	$151.5039	$151.50	$151.50	$151.50
Purchase #3	$138.74	3.831%	$144.0551	$144.06	$144.05	$144.10
Purchase #4	$74.56	4.250%	$77.7288	$77.73	$77.75	$77.70
Purchase #5	$24.64	9.755%	$27.0436	$27.04	$27.05	$27.00
Purchase #6	$204.64	6.594%	$218.134	$218.13	$218.15	$218.10
Purchase #7	$92.51	8.551%	$100.4205	$100.42	$100.40	$100.40
7 purchase totals =	$792.34		$842.6506	$842.64	$842.65	$842.60