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	$44.40	9.457%	$48.5989	$48.60	$48.60	$48.60
Purchase #2	$250.87	4.369%	$261.8305	$261.83	$261.85	$261.80
Purchase #3	$130.83	10.420%	$144.4625	$144.46	$144.45	$144.50
Purchase #4	$242.94	8.845%	$264.428	$264.43	$264.45	$264.40
Purchase #5	$174.44	5.365%	$183.7987	$183.80	$183.80	$183.80
Purchase #6	$43.86	3.149%	$45.2412	$45.24	$45.25	$45.20
Purchase #7	$137.83	5.279%	$145.106	$145.11	$145.10	$145.10
7 purchase totals =	$1,025.17		$1,093.4658	$1,093.47	$1,093.50	$1,093.40