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	$164.44	10.456%	$181.6338	$181.63	$181.65	$181.60
Purchase #2	$136.57	5.602%	$144.2207	$144.22	$144.20	$144.20
Purchase #3	$152.56	7.610%	$164.1698	$164.17	$164.15	$164.20
Purchase #4	$194.28	5.658%	$205.2724	$205.27	$205.25	$205.30
Purchase #5	$184.38	7.640%	$198.4666	$198.47	$198.45	$198.50
Purchase #6	$220.78	6.358%	$234.8172	$234.82	$234.80	$234.80
Purchase #7	$48.87	6.225%	$51.9122	$51.91	$51.90	$51.90
7 purchase totals =	$1,101.88		$1,180.4927	$1,180.49	$1,180.40	$1,180.50