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	$19.26	11.351%	$21.4462	$21.45	$21.45	$21.40
Purchase #2	$42.28	8.388%	$45.8264	$45.83	$45.85	$45.80
Purchase #3	$30.29	13.241%	$34.3007	$34.30	$34.30	$34.30
Purchase #4	$172.68	4.480%	$180.4161	$180.42	$180.40	$180.40
Purchase #5	$49.65	13.305%	$56.2559	$56.26	$56.25	$56.30
Purchase #6	$12.42	9.812%	$13.6387	$13.64	$13.65	$13.60
Purchase #7	$53.38	11.857%	$59.7093	$59.71	$59.70	$59.70
7 purchase totals =	$379.96		$411.5933	$411.61	$411.60	$411.50