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	$10.29	12.143%	$11.5395	$11.54	$11.55	$11.50
Purchase #2	$38.38	9.167%	$41.8983	$41.90	$41.90	$41.90
Purchase #3	$26.34	4.863%	$27.6209	$27.62	$27.60	$27.60
Purchase #4	$60.42	7.480%	$64.9394	$64.94	$64.95	$64.90
Purchase #5	$62.60	3.656%	$64.8887	$64.89	$64.90	$64.90
Purchase #6	$56.61	13.329%	$64.1555	$64.16	$64.15	$64.20
Purchase #7	$138.91	11.616%	$155.0458	$155.05	$155.05	$155.00
7 purchase totals =	$393.55		$430.0881	$430.10	$430.10	$430.00