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	$103.29	7.512%	$111.0491	$111.05	$111.05	$111.00
Purchase #2	$153.74	11.623%	$171.6092	$171.61	$171.60	$171.60
Purchase #3	$10.35	5.866%	$10.9571	$10.96	$10.95	$11.00
Purchase #4	$132.39	8.113%	$143.1308	$143.13	$143.15	$143.10
Purchase #5	$105.55	7.298%	$113.253	$113.25	$113.25	$113.30
Purchase #6	$232.47	8.619%	$252.5066	$252.51	$252.50	$252.50
Purchase #7	$144.69	4.145%	$150.6874	$150.69	$150.70	$150.70
7 purchase totals =	$882.48		$953.1932	$953.20	$953.20	$953.20