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	$149.91	13.234%	$169.7491	$169.75	$169.75	$169.70
Purchase #2	$117.77	7.861%	$127.0279	$127.03	$127.05	$127.00
Purchase #3	$72.44	4.189%	$75.4745	$75.47	$75.45	$75.50
Purchase #4	$193.71	10.595%	$214.2336	$214.23	$214.25	$214.20
Purchase #5	$239.66	11.645%	$267.5684	$267.57	$267.55	$267.60
Purchase #6	$83.56	6.707%	$89.1644	$89.16	$89.15	$89.20
Purchase #7	$48.47	11.487%	$54.0377	$54.04	$54.05	$54.00
7 purchase totals =	$905.52		$997.2556	$997.25	$997.25	$997.20