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	$215.72	7.321%	$231.5129	$231.51	$231.50	$231.50
Purchase #2	$128.58	13.521%	$145.9653	$145.97	$145.95	$146.00
Purchase #3	$22.32	5.723%	$23.5974	$23.60	$23.60	$23.60
Purchase #4	$121.40	7.771%	$130.834	$130.83	$130.85	$130.80
Purchase #5	$199.90	11.682%	$223.2523	$223.25	$223.25	$223.30
Purchase #6	$90.65	9.343%	$99.1194	$99.12	$99.10	$99.10
Purchase #7	$150.77	5.541%	$159.1242	$159.12	$159.10	$159.10
7 purchase totals =	$929.34		$1,013.4055	$1,013.40	$1,013.35	$1,013.40