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	$151.25	4.559%	$158.1455	$158.15	$158.15	$158.10
Purchase #2	$14.82	6.727%	$15.8169	$15.82	$15.80	$15.80
Purchase #3	$66.44	9.125%	$72.5027	$72.50	$72.50	$72.50
Purchase #4	$227.58	7.150%	$243.852	$243.85	$243.85	$243.90
Purchase #5	$231.36	8.647%	$251.3657	$251.37	$251.35	$251.40
Purchase #6	$124.29	7.480%	$133.5869	$133.59	$133.60	$133.60
Purchase #7	$61.89	6.406%	$65.8547	$65.85	$65.85	$65.90
7 purchase totals =	$877.63		$941.1244	$941.13	$941.10	$941.20