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	$142.58	13.659%	$162.055	$162.06	$162.05	$162.10
Purchase #2	$66.80	5.419%	$70.4199	$70.42	$70.40	$70.40
Purchase #3	$60.37	6.560%	$64.3303	$64.33	$64.35	$64.30
Purchase #4	$63.96	3.797%	$66.3886	$66.39	$66.40	$66.40
Purchase #5	$155.77	10.678%	$172.4031	$172.40	$172.40	$172.40
Purchase #6	$81.28	10.852%	$90.1005	$90.10	$90.10	$90.10
Purchase #7	$218.86	8.834%	$238.1941	$238.19	$238.20	$238.20
7 purchase totals =	$789.62		$863.8915	$863.89	$863.90	$863.90