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	$53.59	10.158%	$59.0337	$59.03	$59.05	$59.00
Purchase #2	$221.26	7.624%	$238.1289	$238.13	$238.15	$238.10
Purchase #3	$248.68	11.646%	$277.6413	$277.64	$277.65	$277.60
Purchase #4	$32.80	8.510%	$35.5913	$35.59	$35.60	$35.60
Purchase #5	$185.64	5.167%	$195.232	$195.23	$195.25	$195.20
Purchase #6	$146.72	4.528%	$153.3635	$153.36	$153.35	$153.40
Purchase #7	$224.49	5.694%	$237.2725	$237.27	$237.25	$237.30
7 purchase totals =	$1,113.18		$1,196.2632	$1,196.25	$1,196.30	$1,196.20