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	$164.35	13.364%	$186.3137	$186.31	$186.30	$186.30
Purchase #2	$97.98	13.806%	$111.5071	$111.51	$111.50	$111.50
Purchase #3	$9.59	10.495%	$10.5965	$10.60	$10.60	$10.60
Purchase #4	$121.86	6.819%	$130.1696	$130.17	$130.15	$130.20
Purchase #5	$64.78	9.448%	$70.9004	$70.90	$70.90	$70.90
Purchase #6	$215.73	12.321%	$242.3101	$242.31	$242.30	$242.30
Purchase #7	$128.32	12.381%	$144.2073	$144.21	$144.20	$144.20
7 purchase totals =	$802.61		$896.0047	$896.01	$895.95	$896.00