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	$162.34	4.178%	$169.1226	$169.12	$169.10	$169.10
Purchase #2	$88.33	4.810%	$92.5787	$92.58	$92.60	$92.60
Purchase #3	$40.58	6.130%	$43.0676	$43.07	$43.05	$43.10
Purchase #4	$145.37	11.390%	$161.9276	$161.93	$161.95	$161.90
Purchase #5	$79.36	13.337%	$89.9442	$89.94	$89.95	$89.90
Purchase #6	$134.82	5.149%	$141.7619	$141.76	$141.75	$141.80
Purchase #7	$149.76	10.463%	$165.4294	$165.43	$165.45	$165.40
7 purchase totals =	$800.56		$863.8320	$863.83	$863.85	$863.80