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	$159.43	3.246%	$164.6051	$164.61	$164.60	$164.60
Purchase #2	$18.61	9.594%	$20.3954	$20.40	$20.40	$20.40
Purchase #3	$155.32	10.867%	$172.1986	$172.20	$172.20	$172.20
Purchase #4	$230.55	7.515%	$247.8758	$247.88	$247.90	$247.90
Purchase #5	$55.38	3.426%	$57.2773	$57.28	$57.30	$57.30
Purchase #6	$30.40	10.654%	$33.6388	$33.64	$33.65	$33.60
Purchase #7	$45.59	9.304%	$49.8317	$49.83	$49.85	$49.80
7 purchase totals =	$695.28		$745.8227	$745.84	$745.90	$745.80