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	$246.59	7.406%	$264.8525	$264.85	$264.85	$264.90
Purchase #2	$236.80	10.365%	$261.3443	$261.34	$261.35	$261.30
Purchase #3	$239.75	11.126%	$266.4246	$266.42	$266.40	$266.40
Purchase #4	$9.83	4.866%	$10.3083	$10.31	$10.30	$10.30
Purchase #5	$214.56	4.177%	$223.5222	$223.52	$223.50	$223.50
Purchase #6	$247.30	9.424%	$270.6056	$270.61	$270.60	$270.60
Purchase #7	$117.60	8.394%	$127.4713	$127.47	$127.45	$127.50
7 purchase totals =	$1,312.43		$1,424.5288	$1,424.52	$1,424.45	$1,424.50