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	$140.99	3.139%	$145.4157	$145.42	$145.40	$145.40
Purchase #2	$55.42	8.152%	$59.9378	$59.94	$59.95	$59.90
Purchase #3	$25.68	3.290%	$26.5249	$26.52	$26.50	$26.50
Purchase #4	$116.49	9.156%	$127.1558	$127.16	$127.15	$127.20
Purchase #5	$88.49	12.679%	$99.7096	$99.71	$99.70	$99.70
Purchase #6	$126.40	4.792%	$132.4571	$132.46	$132.45	$132.50
Purchase #7	$146.81	12.766%	$165.5518	$165.55	$165.55	$165.60
7 purchase totals =	$700.28		$756.7527	$756.76	$756.70	$756.80