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	$201.67	6.793%	$215.3694	$215.37	$215.35	$215.40
Purchase #2	$100.70	10.801%	$111.5766	$111.58	$111.60	$111.60
Purchase #3	$127.70	3.487%	$132.1529	$132.15	$132.15	$132.20
Purchase #4	$92.25	13.702%	$104.8901	$104.89	$104.90	$104.90
Purchase #5	$33.31	3.740%	$34.5558	$34.56	$34.55	$34.60
Purchase #6	$244.95	10.377%	$270.3685	$270.37	$270.35	$270.40
Purchase #7	$101.87	6.186%	$108.1717	$108.17	$108.15	$108.20
7 purchase totals =	$902.45		$977.0850	$977.09	$977.05	$977.30