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	$215.43	4.143%	$224.3553	$224.36	$224.35	$224.40
Purchase #2	$100.96	10.554%	$111.6153	$111.62	$111.60	$111.60
Purchase #3	$141.56	7.659%	$152.4021	$152.40	$152.40	$152.40
Purchase #4	$241.63	6.332%	$256.93	$256.93	$256.95	$256.90
Purchase #5	$215.60	8.242%	$233.3698	$233.37	$233.35	$233.40
Purchase #6	$87.47	13.784%	$99.5269	$99.53	$99.55	$99.50
Purchase #7	$36.43	9.380%	$39.8471	$39.85	$39.85	$39.80
7 purchase totals =	$1,039.08		$1,118.0465	$1,118.06	$1,118.05	$1,118.00