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	$215.96	10.232%	$238.057	$238.06	$238.05	$238.10
Purchase #2	$172.54	4.858%	$180.922	$180.92	$180.90	$180.90
Purchase #3	$185.59	7.325%	$199.1845	$199.18	$199.20	$199.20
Purchase #4	$198.50	3.454%	$205.3562	$205.36	$205.35	$205.40
Purchase #5	$52.90	13.436%	$60.0076	$60.01	$60.00	$60.00
Purchase #6	$16.61	10.176%	$18.3002	$18.30	$18.30	$18.30
Purchase #7	$80.35	13.190%	$90.9482	$90.95	$90.95	$90.90
7 purchase totals =	$922.45		$992.7757	$992.78	$992.75	$992.80