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	$219.65	10.306%	$242.2871	$242.29	$242.30	$242.30
Purchase #2	$243.35	6.380%	$258.8757	$258.88	$258.90	$258.90
Purchase #3	$60.54	10.460%	$66.8725	$66.87	$66.85	$66.90
Purchase #4	$25.78	6.621%	$27.4869	$27.49	$27.50	$27.50
Purchase #5	$35.74	6.733%	$38.1464	$38.15	$38.15	$38.10
Purchase #6	$172.73	10.301%	$190.5229	$190.52	$190.50	$190.50
Purchase #7	$214.93	9.210%	$234.7251	$234.73	$234.75	$234.70
7 purchase totals =	$972.72		$1,058.9166	$1,058.93	$1,058.95	$1,058.90