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	$120.49	8.287%	$130.475	$130.48	$130.50	$130.50
Purchase #2	$104.41	11.757%	$116.6855	$116.69	$116.70	$116.70
Purchase #3	$151.61	13.716%	$172.4048	$172.40	$172.40	$172.40
Purchase #4	$212.86	5.585%	$224.7482	$224.75	$224.75	$224.70
Purchase #5	$92.91	12.583%	$104.6009	$104.60	$104.60	$104.60
Purchase #6	$202.79	11.338%	$225.7823	$225.78	$225.80	$225.80
Purchase #7	$158.60	6.227%	$168.476	$168.48	$168.50	$168.50
7 purchase totals =	$1,043.67		$1,143.1727	$1,143.18	$1,143.25	$1,143.20