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	$79.44	7.594%	$85.4727	$85.47	$85.45	$85.50
Purchase #2	$124.77	11.451%	$139.0574	$139.06	$139.05	$139.10
Purchase #3	$129.50	7.816%	$139.6217	$139.62	$139.60	$139.60
Purchase #4	$194.63	3.643%	$201.7204	$201.72	$201.70	$201.70
Purchase #5	$137.92	5.248%	$145.158	$145.16	$145.15	$145.20
Purchase #6	$235.97	6.262%	$250.7464	$250.75	$250.75	$250.70
Purchase #7	$99.33	6.374%	$105.6613	$105.66	$105.65	$105.70
7 purchase totals =	$1,001.56		$1,067.4379	$1,067.44	$1,067.35	$1,067.50