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	$129.42	12.706%	$145.8641	$145.86	$145.85	$145.90
Purchase #2	$205.60	8.390%	$222.8498	$222.85	$222.85	$222.80
Purchase #3	$140.69	8.852%	$153.1439	$153.14	$153.15	$153.10
Purchase #4	$55.50	5.784%	$58.7101	$58.71	$58.70	$58.70
Purchase #5	$140.61	6.191%	$149.3152	$149.32	$149.30	$149.30
Purchase #6	$101.29	3.578%	$104.9142	$104.91	$104.90	$104.90
Purchase #7	$247.88	6.817%	$264.778	$264.78	$264.80	$264.80
7 purchase totals =	$1,020.99		$1,099.5753	$1,099.57	$1,099.55	$1,099.50