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	$219.72	13.225%	$248.778	$248.78	$248.80	$248.80
Purchase #2	$156.99	9.432%	$171.7973	$171.80	$171.80	$171.80
Purchase #3	$166.45	4.188%	$173.4209	$173.42	$173.40	$173.40
Purchase #4	$159.72	11.629%	$178.2938	$178.29	$178.30	$178.30
Purchase #5	$60.55	6.316%	$64.3743	$64.37	$64.35	$64.40
Purchase #6	$105.65	6.408%	$112.4201	$112.42	$112.40	$112.40
Purchase #7	$48.93	8.530%	$53.1037	$53.10	$53.10	$53.10
7 purchase totals =	$918.01		$1,002.1881	$1,002.18	$1,002.15	$1,002.20