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	$111.52	10.153%	$122.8426	$122.84	$122.85	$122.80
Purchase #2	$36.89	6.440%	$39.2657	$39.27	$39.25	$39.30
Purchase #3	$42.77	7.487%	$45.9722	$45.97	$45.95	$46.00
Purchase #4	$92.59	9.726%	$101.5953	$101.60	$101.60	$101.60
Purchase #5	$190.60	13.631%	$216.5807	$216.58	$216.60	$216.60
Purchase #6	$34.43	7.154%	$36.8931	$36.89	$36.90	$36.90
Purchase #7	$107.33	3.566%	$111.1574	$111.16	$111.15	$111.20
7 purchase totals =	$616.13		$674.3070	$674.31	$674.30	$674.40