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	$106.52	4.476%	$111.2878	$111.29	$111.30	$111.30
Purchase #2	$127.85	11.199%	$142.1679	$142.17	$142.15	$142.20
Purchase #3	$75.53	4.443%	$78.8858	$78.89	$78.90	$78.90
Purchase #4	$184.79	5.301%	$194.5857	$194.59	$194.60	$194.60
Purchase #5	$206.61	3.578%	$214.0025	$214.00	$214.00	$214.00
Purchase #6	$79.43	9.206%	$86.7423	$86.74	$86.75	$86.70
Purchase #7	$97.52	4.335%	$101.7475	$101.75	$101.75	$101.70
7 purchase totals =	$878.25		$929.4195	$929.43	$929.45	$929.40