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	$156.88	10.377%	$173.1594	$173.16	$173.15	$173.20
Purchase #2	$26.52	3.826%	$27.5347	$27.53	$27.55	$27.50
Purchase #3	$175.84	7.506%	$189.0386	$189.04	$189.05	$189.00
Purchase #4	$44.74	5.342%	$47.13	$47.13	$47.15	$47.10
Purchase #5	$88.58	9.251%	$96.7745	$96.77	$96.75	$96.80
Purchase #6	$142.86	5.785%	$151.1245	$151.12	$151.10	$151.10
Purchase #7	$56.25	5.719%	$59.4669	$59.47	$59.45	$59.50
7 purchase totals =	$691.67		$744.2286	$744.22	$744.20	$744.20