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	$209.83	8.385%	$227.4242	$227.42	$227.40	$227.40
Purchase #2	$186.54	13.129%	$211.0308	$211.03	$211.05	$211.00
Purchase #3	$139.83	7.449%	$150.2459	$150.25	$150.25	$150.20
Purchase #4	$152.56	13.552%	$173.2349	$173.23	$173.25	$173.20
Purchase #5	$55.30	11.773%	$61.8105	$61.81	$61.80	$61.80
Purchase #6	$230.41	3.643%	$238.8038	$238.80	$238.80	$238.80
Purchase #7	$8.53	5.226%	$8.9758	$8.98	$9.00	$9.00
7 purchase totals =	$983.00		$1,071.5259	$1,071.52	$1,071.55	$1,071.40