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	$165.72	5.737%	$175.2274	$175.23	$175.25	$175.20
Purchase #2	$10.27	6.757%	$10.9639	$10.96	$10.95	$11.00
Purchase #3	$91.99	13.470%	$104.3811	$104.38	$104.40	$104.40
Purchase #4	$10.69	10.303%	$11.7914	$11.79	$11.80	$11.80
Purchase #5	$138.90	8.427%	$150.6051	$150.61	$150.60	$150.60
Purchase #6	$101.89	7.395%	$109.4248	$109.42	$109.40	$109.40
Purchase #7	$9.44	7.724%	$10.1691	$10.17	$10.15	$10.20
7 purchase totals =	$528.90		$572.5628	$572.56	$572.55	$572.60