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	$222.60	13.670%	$253.0294	$253.03	$253.05	$253.00
Purchase #2	$88.54	13.156%	$100.1883	$100.19	$100.20	$100.20
Purchase #3	$48.30	13.327%	$54.7369	$54.74	$54.75	$54.70
Purchase #4	$6.64	9.385%	$7.2632	$7.26	$7.25	$7.30
Purchase #5	$131.45	12.269%	$147.5776	$147.58	$147.60	$147.60
Purchase #6	$111.52	4.249%	$116.2585	$116.26	$116.25	$116.30
Purchase #7	$136.29	7.604%	$146.6535	$146.65	$146.65	$146.70
7 purchase totals =	$745.34		$825.7074	$825.71	$825.75	$825.80