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	$149.49	11.751%	$167.0566	$167.06	$167.05	$167.10
Purchase #2	$127.40	8.779%	$138.5844	$138.58	$138.60	$138.60
Purchase #3	$32.58	5.832%	$34.4801	$34.48	$34.50	$34.50
Purchase #4	$104.32	13.766%	$118.6807	$118.68	$118.70	$118.70
Purchase #5	$40.31	4.719%	$42.2122	$42.21	$42.20	$42.20
Purchase #6	$35.88	4.106%	$37.3532	$37.35	$37.35	$37.40
Purchase #7	$20.85	9.457%	$22.8218	$22.82	$22.80	$22.80
7 purchase totals =	$510.83		$561.1890	$561.18	$561.20	$561.30