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	$162.49	8.106%	$175.6614	$175.66	$175.65	$175.70
Purchase #2	$222.77	12.389%	$250.369	$250.37	$250.35	$250.40
Purchase #3	$15.27	13.240%	$17.2917	$17.29	$17.30	$17.30
Purchase #4	$90.82	7.367%	$97.5107	$97.51	$97.50	$97.50
Purchase #5	$133.27	8.406%	$144.4727	$144.47	$144.45	$144.50
Purchase #6	$88.42	12.103%	$99.1215	$99.12	$99.10	$99.10
Purchase #7	$164.54	3.825%	$170.8337	$170.83	$170.85	$170.80
7 purchase totals =	$877.58		$955.2607	$955.25	$955.20	$955.30