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	$199.71	3.577%	$206.8536	$206.85	$206.85	$206.90
Purchase #2	$69.67	13.628%	$79.1646	$79.16	$79.15	$79.20
Purchase #3	$48.32	13.556%	$54.8703	$54.87	$54.85	$54.90
Purchase #4	$147.38	12.111%	$165.2292	$165.23	$165.25	$165.20
Purchase #5	$151.28	8.707%	$164.4519	$164.45	$164.45	$164.50
Purchase #6	$143.62	6.624%	$153.1334	$153.13	$153.15	$153.10
Purchase #7	$244.81	12.476%	$275.3525	$275.35	$275.35	$275.40
7 purchase totals =	$1,004.79		$1,099.0555	$1,099.04	$1,099.05	$1,099.20