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	$233.71	12.269%	$262.3839	$262.38	$262.40	$262.40
Purchase #2	$199.31	13.589%	$226.3942	$226.39	$226.40	$226.40
Purchase #3	$169.69	5.198%	$178.5105	$178.51	$178.50	$178.50
Purchase #4	$52.32	11.563%	$58.3698	$58.37	$58.35	$58.40
Purchase #5	$79.49	10.169%	$87.5733	$87.57	$87.55	$87.60
Purchase #6	$153.56	12.546%	$172.8256	$172.83	$172.85	$172.80
Purchase #7	$172.78	6.805%	$184.5377	$184.54	$184.55	$184.50
7 purchase totals =	$1,060.86		$1,170.5950	$1,170.59	$1,170.60	$1,170.60