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	$158.42	4.493%	$165.5378	$165.54	$165.55	$165.50
Purchase #2	$50.26	11.228%	$55.9032	$55.90	$55.90	$55.90
Purchase #3	$142.79	7.215%	$153.0923	$153.09	$153.10	$153.10
Purchase #4	$53.32	3.560%	$55.2182	$55.22	$55.20	$55.20
Purchase #5	$101.84	9.635%	$111.6523	$111.65	$111.65	$111.70
Purchase #6	$40.47	6.183%	$42.9723	$42.97	$42.95	$43.00
Purchase #7	$45.71	3.555%	$47.335	$47.34	$47.35	$47.30
7 purchase totals =	$592.81		$631.7111	$631.71	$631.70	$631.70