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	$123.34	3.531%	$127.6951	$127.70	$127.70	$127.70
Purchase #2	$177.92	3.569%	$184.27	$184.27	$184.25	$184.30
Purchase #3	$95.83	10.184%	$105.5893	$105.59	$105.60	$105.60
Purchase #4	$107.30	9.551%	$117.5482	$117.55	$117.55	$117.50
Purchase #5	$33.38	7.370%	$35.8401	$35.84	$35.85	$35.80
Purchase #6	$130.85	12.271%	$146.9066	$146.91	$146.90	$146.90
Purchase #7	$6.49	3.237%	$6.7001	$6.70	$6.70	$6.70
7 purchase totals =	$675.11		$724.5494	$724.56	$724.55	$724.50