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	$92.76	13.331%	$105.1258	$105.13	$105.15	$105.10
Purchase #2	$9.25	7.705%	$9.9627	$9.96	$9.95	$10.00
Purchase #3	$171.42	8.273%	$185.6016	$185.60	$185.60	$185.60
Purchase #4	$17.78	5.510%	$18.7597	$18.76	$18.75	$18.80
Purchase #5	$223.55	9.461%	$244.7001	$244.70	$244.70	$244.70
Purchase #6	$111.77	13.773%	$127.1641	$127.16	$127.15	$127.20
Purchase #7	$98.91	6.834%	$105.6695	$105.67	$105.65	$105.70
7 purchase totals =	$725.44		$796.9835	$796.98	$796.95	$797.10