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	$64.39	3.137%	$66.4099	$66.41	$66.40	$66.40
Purchase #2	$244.89	11.626%	$273.3609	$273.36	$273.35	$273.40
Purchase #3	$141.39	4.694%	$148.0268	$148.03	$148.05	$148.00
Purchase #4	$138.31	5.363%	$145.7276	$145.73	$145.75	$145.70
Purchase #5	$75.92	10.455%	$83.8574	$83.86	$83.85	$83.90
Purchase #6	$233.42	11.767%	$260.8865	$260.89	$260.90	$260.90
Purchase #7	$129.92	12.825%	$146.5822	$146.58	$146.60	$146.60
7 purchase totals =	$1,028.24		$1,124.8513	$1,124.86	$1,124.90	$1,124.90