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	$133.92	8.622%	$145.4666	$145.47	$145.45	$145.50
Purchase #2	$20.48	3.620%	$21.2214	$21.22	$21.20	$21.20
Purchase #3	$200.29	11.120%	$222.5622	$222.56	$222.55	$222.60
Purchase #4	$150.27	5.319%	$158.2629	$158.26	$158.25	$158.30
Purchase #5	$177.45	11.487%	$197.8337	$197.83	$197.85	$197.80
Purchase #6	$59.86	3.485%	$61.9461	$61.95	$61.95	$61.90
Purchase #7	$238.74	13.784%	$271.6479	$271.65	$271.65	$271.60
7 purchase totals =	$981.01		$1,078.9408	$1,078.94	$1,078.90	$1,078.90