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	$91.35	13.525%	$103.7051	$103.71	$103.70	$103.70
Purchase #2	$52.74	3.320%	$54.491	$54.49	$54.50	$54.50
Purchase #3	$149.91	4.375%	$156.4686	$156.47	$156.45	$156.50
Purchase #4	$228.66	7.301%	$245.3545	$245.35	$245.35	$245.40
Purchase #5	$135.93	11.111%	$151.0332	$151.03	$151.05	$151.00
Purchase #6	$9.27	9.130%	$10.1164	$10.12	$10.10	$10.10
Purchase #7	$74.34	5.560%	$78.4733	$78.47	$78.45	$78.50
7 purchase totals =	$742.20		$799.6421	$799.64	$799.60	$799.70