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	$230.29	13.732%	$261.9134	$261.91	$261.90	$261.90
Purchase #2	$54.72	3.541%	$56.6576	$56.66	$56.65	$56.70
Purchase #3	$56.56	4.569%	$59.1442	$59.14	$59.15	$59.10
Purchase #4	$109.29	6.319%	$116.196	$116.20	$116.20	$116.20
Purchase #5	$148.86	7.245%	$159.6449	$159.64	$159.65	$159.60
Purchase #6	$127.49	12.400%	$143.2988	$143.30	$143.30	$143.30
Purchase #7	$179.62	10.491%	$198.4639	$198.46	$198.45	$198.50
7 purchase totals =	$906.83		$995.3188	$995.31	$995.30	$995.30