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	$83.94	4.111%	$87.3908	$87.39	$87.40	$87.40
Purchase #2	$197.68	8.630%	$214.7398	$214.74	$214.75	$214.70
Purchase #3	$88.77	13.627%	$100.8667	$100.87	$100.85	$100.90
Purchase #4	$123.51	7.246%	$132.4595	$132.46	$132.45	$132.50
Purchase #5	$146.97	9.278%	$160.6059	$160.61	$160.60	$160.60
Purchase #6	$165.91	11.674%	$185.2783	$185.28	$185.30	$185.30
Purchase #7	$13.55	10.146%	$14.9248	$14.92	$14.90	$14.90
7 purchase totals =	$820.33		$896.2658	$896.27	$896.25	$896.30