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	$36.52	4.278%	$38.0823	$38.08	$38.10	$38.10
Purchase #2	$9.93	9.759%	$10.8991	$10.90	$10.90	$10.90
Purchase #3	$132.72	3.793%	$137.7541	$137.75	$137.75	$137.80
Purchase #4	$172.32	4.176%	$179.5161	$179.52	$179.50	$179.50
Purchase #5	$130.41	7.634%	$140.3655	$140.37	$140.35	$140.40
Purchase #6	$235.89	8.622%	$256.2284	$256.23	$256.25	$256.20
Purchase #7	$184.92	8.337%	$200.3368	$200.34	$200.35	$200.30
7 purchase totals =	$902.71		$963.1823	$963.19	$963.20	$963.20