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	$55.45	10.322%	$61.1735	$61.17	$61.15	$61.20
Purchase #2	$120.39	3.557%	$124.6723	$124.67	$124.65	$124.70
Purchase #3	$32.83	13.541%	$37.2755	$37.28	$37.30	$37.30
Purchase #4	$83.93	11.123%	$93.2655	$93.27	$93.25	$93.30
Purchase #5	$108.53	9.136%	$118.4453	$118.45	$118.45	$118.40
Purchase #6	$62.29	13.311%	$70.5814	$70.58	$70.60	$70.60
Purchase #7	$103.60	7.136%	$110.9929	$110.99	$111.00	$111.00
7 purchase totals =	$567.02		$616.4064	$616.41	$616.40	$616.50