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	$98.99	6.777%	$105.6986	$105.70	$105.70	$105.70
Purchase #2	$176.63	5.154%	$185.7335	$185.73	$185.75	$185.70
Purchase #3	$7.77	7.480%	$8.3512	$8.35	$8.35	$8.40
Purchase #4	$33.98	10.384%	$37.5085	$37.51	$37.50	$37.50
Purchase #5	$68.30	12.828%	$77.0615	$77.06	$77.05	$77.10
Purchase #6	$137.83	6.238%	$146.4278	$146.43	$146.45	$146.40
Purchase #7	$140.84	12.601%	$158.5872	$158.59	$158.60	$158.60
7 purchase totals =	$664.34		$719.3683	$719.37	$719.40	$719.40