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	$142.72	11.730%	$159.4611	$159.46	$159.45	$159.50
Purchase #2	$149.38	11.569%	$166.6618	$166.66	$166.65	$166.70
Purchase #3	$93.88	6.417%	$99.9043	$99.90	$99.90	$99.90
Purchase #4	$87.37	4.309%	$91.1348	$91.13	$91.15	$91.10
Purchase #5	$35.31	11.414%	$39.3403	$39.34	$39.35	$39.30
Purchase #6	$120.78	5.747%	$127.7212	$127.72	$127.70	$127.70
Purchase #7	$21.46	5.196%	$22.5751	$22.58	$22.60	$22.60
7 purchase totals =	$650.90		$706.7986	$706.79	$706.80	$706.80