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	$92.59	13.833%	$105.398	$105.40	$105.40	$105.40
Purchase #2	$152.45	3.707%	$158.1013	$158.10	$158.10	$158.10
Purchase #3	$168.28	7.170%	$180.3457	$180.35	$180.35	$180.30
Purchase #4	$222.89	4.667%	$233.2923	$233.29	$233.30	$233.30
Purchase #5	$111.62	4.438%	$116.5737	$116.57	$116.55	$116.60
Purchase #6	$226.61	10.109%	$249.518	$249.52	$249.50	$249.50
Purchase #7	$148.82	5.769%	$157.4054	$157.41	$157.40	$157.40
7 purchase totals =	$1,123.26		$1,200.6344	$1,200.64	$1,200.60	$1,200.60