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	$192.88	12.217%	$216.4441	$216.44	$216.45	$216.40
Purchase #2	$145.74	11.266%	$162.1591	$162.16	$162.15	$162.20
Purchase #3	$145.64	8.698%	$158.3078	$158.31	$158.30	$158.30
Purchase #4	$71.60	12.856%	$80.8049	$80.80	$80.80	$80.80
Purchase #5	$44.49	6.196%	$47.2466	$47.25	$47.25	$47.20
Purchase #6	$72.37	5.718%	$76.5081	$76.51	$76.50	$76.50
Purchase #7	$122.44	4.256%	$127.651	$127.65	$127.65	$127.70
7 purchase totals =	$795.16		$869.1216	$869.12	$869.10	$869.10