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	$53.51	10.495%	$59.1259	$59.13	$59.15	$59.10
Purchase #2	$171.66	3.689%	$177.9925	$177.99	$178.00	$178.00
Purchase #3	$149.28	6.409%	$158.8474	$158.85	$158.85	$158.80
Purchase #4	$40.86	5.675%	$43.1788	$43.18	$43.20	$43.20
Purchase #5	$33.56	10.681%	$37.1445	$37.14	$37.15	$37.10
Purchase #6	$175.46	8.196%	$189.8407	$189.84	$189.85	$189.80
Purchase #7	$46.95	3.194%	$48.4496	$48.45	$48.45	$48.40
7 purchase totals =	$671.28		$714.5794	$714.58	$714.65	$714.40