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	$229.38	11.746%	$256.323	$256.32	$256.30	$256.30
Purchase #2	$211.82	7.270%	$227.2193	$227.22	$227.20	$227.20
Purchase #3	$47.63	11.210%	$52.9693	$52.97	$52.95	$53.00
Purchase #4	$158.73	3.599%	$164.4427	$164.44	$164.45	$164.40
Purchase #5	$231.51	5.451%	$244.1296	$244.13	$244.15	$244.10
Purchase #6	$46.87	11.624%	$52.3182	$52.32	$52.30	$52.30
Purchase #7	$100.83	10.495%	$111.4121	$111.41	$111.40	$111.40
7 purchase totals =	$1,026.77		$1,108.8142	$1,108.81	$1,108.75	$1,108.70