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	$179.60	8.138%	$194.2158	$194.22	$194.20	$194.20
Purchase #2	$228.61	12.314%	$256.761	$256.76	$256.75	$256.80
Purchase #3	$99.55	5.438%	$104.9635	$104.96	$104.95	$105.00
Purchase #4	$157.56	9.772%	$172.9568	$172.96	$172.95	$173.00
Purchase #5	$16.97	3.448%	$17.5551	$17.56	$17.55	$17.60
Purchase #6	$152.37	10.277%	$168.0291	$168.03	$168.05	$168.00
Purchase #7	$231.86	11.222%	$257.8793	$257.88	$257.90	$257.90
7 purchase totals =	$1,066.52		$1,172.3606	$1,172.37	$1,172.35	$1,172.50