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	$103.38	7.467%	$111.0994	$111.10	$111.10	$111.10
Purchase #2	$122.89	13.268%	$139.195	$139.20	$139.20	$139.20
Purchase #3	$92.55	12.229%	$103.8679	$103.87	$103.85	$103.90
Purchase #4	$152.97	6.699%	$163.2175	$163.22	$163.20	$163.20
Purchase #5	$80.31	7.272%	$86.1501	$86.15	$86.15	$86.20
Purchase #6	$45.29	10.635%	$50.1066	$50.11	$50.10	$50.10
Purchase #7	$127.49	5.460%	$134.451	$134.45	$134.45	$134.50
7 purchase totals =	$724.88		$788.0875	$788.10	$788.05	$788.20