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	$48.66	11.807%	$54.4053	$54.41	$54.40	$54.40
Purchase #2	$226.71	7.752%	$244.2846	$244.28	$244.30	$244.30
Purchase #3	$59.59	12.151%	$66.8308	$66.83	$66.85	$66.80
Purchase #4	$174.31	7.442%	$187.2822	$187.28	$187.30	$187.30
Purchase #5	$97.32	13.324%	$110.2869	$110.29	$110.30	$110.30
Purchase #6	$80.84	5.373%	$85.1835	$85.18	$85.20	$85.20
Purchase #7	$132.50	3.406%	$137.013	$137.01	$137.00	$137.00
7 purchase totals =	$819.93		$885.2863	$885.28	$885.35	$885.30