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	$145.62	12.861%	$164.3482	$164.35	$164.35	$164.30
Purchase #2	$135.84	3.144%	$140.1108	$140.11	$140.10	$140.10
Purchase #3	$172.63	6.631%	$184.0771	$184.08	$184.10	$184.10
Purchase #4	$30.69	4.684%	$32.1275	$32.13	$32.15	$32.10
Purchase #5	$153.77	7.554%	$165.3858	$165.39	$165.40	$165.40
Purchase #6	$104.56	13.308%	$118.4748	$118.47	$118.45	$118.50
Purchase #7	$64.78	12.154%	$72.6534	$72.65	$72.65	$72.70
7 purchase totals =	$807.89		$877.1776	$877.18	$877.20	$877.20