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	$64.68	3.429%	$66.8979	$66.90	$66.90	$66.90
Purchase #2	$148.35	7.795%	$159.9139	$159.91	$159.90	$159.90
Purchase #3	$175.92	7.453%	$189.0313	$189.03	$189.05	$189.00
Purchase #4	$104.28	7.261%	$111.8518	$111.85	$111.85	$111.90
Purchase #5	$220.60	4.833%	$231.2616	$231.26	$231.25	$231.30
Purchase #6	$147.97	11.831%	$165.4763	$165.48	$165.50	$165.50
Purchase #7	$105.80	5.442%	$111.5576	$111.56	$111.55	$111.60
7 purchase totals =	$967.60		$1,035.9904	$1,035.99	$1,036.00	$1,036.10