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	$214.77	6.244%	$228.1802	$228.18	$228.20	$228.20
Purchase #2	$144.59	3.851%	$150.1582	$150.16	$150.15	$150.20
Purchase #3	$105.68	5.368%	$111.3529	$111.35	$111.35	$111.40
Purchase #4	$73.94	11.324%	$82.313	$82.31	$82.30	$82.30
Purchase #5	$5.38	12.747%	$6.0658	$6.07	$6.05	$6.10
Purchase #6	$125.45	5.504%	$132.3548	$132.35	$132.35	$132.40
Purchase #7	$75.51	4.234%	$78.7071	$78.71	$78.70	$78.70
7 purchase totals =	$745.32		$789.1320	$789.13	$789.10	$789.30