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	$160.29	8.321%	$173.6277	$173.63	$173.65	$173.60
Purchase #2	$131.77	11.260%	$146.6073	$146.61	$146.60	$146.60
Purchase #3	$51.93	3.865%	$53.9371	$53.94	$53.95	$53.90
Purchase #4	$10.65	6.212%	$11.3116	$11.31	$11.30	$11.30
Purchase #5	$40.42	3.422%	$41.8032	$41.80	$41.80	$41.80
Purchase #6	$243.27	8.497%	$263.9407	$263.94	$263.95	$263.90
Purchase #7	$109.30	12.672%	$123.1505	$123.15	$123.15	$123.20
7 purchase totals =	$747.63		$814.3781	$814.38	$814.40	$814.30