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	$20.68	10.405%	$22.8318	$22.83	$22.85	$22.80
Purchase #2	$34.52	7.578%	$37.1359	$37.14	$37.15	$37.10
Purchase #3	$36.32	10.390%	$40.0936	$40.09	$40.10	$40.10
Purchase #4	$101.72	7.540%	$109.3897	$109.39	$109.40	$109.40
Purchase #5	$137.32	3.197%	$141.7101	$141.71	$141.70	$141.70
Purchase #6	$210.29	11.497%	$234.467	$234.47	$234.45	$234.50
Purchase #7	$46.63	10.406%	$51.4823	$51.48	$51.50	$51.50
7 purchase totals =	$587.48		$637.1104	$637.11	$637.15	$637.10