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	$227.82	4.675%	$238.4706	$238.47	$238.45	$238.50
Purchase #2	$173.39	12.654%	$195.3308	$195.33	$195.35	$195.30
Purchase #3	$141.76	6.633%	$151.1629	$151.16	$151.15	$151.20
Purchase #4	$237.82	5.657%	$251.2735	$251.27	$251.25	$251.30
Purchase #5	$208.66	6.750%	$222.7446	$222.74	$222.75	$222.70
Purchase #6	$76.90	3.493%	$79.5861	$79.59	$79.60	$79.60
Purchase #7	$38.31	8.547%	$41.5844	$41.58	$41.60	$41.60
7 purchase totals =	$1,104.66		$1,180.1529	$1,180.14	$1,180.15	$1,180.20