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	$97.46	6.284%	$103.5844	$103.58	$103.60	$103.60
Purchase #2	$46.41	4.408%	$48.4558	$48.46	$48.45	$48.50
Purchase #3	$40.59	4.178%	$42.2859	$42.29	$42.30	$42.30
Purchase #4	$29.63	4.680%	$31.0167	$31.02	$31.00	$31.00
Purchase #5	$226.76	13.280%	$256.8737	$256.87	$256.85	$256.90
Purchase #6	$16.89	4.108%	$17.5838	$17.58	$17.60	$17.60
Purchase #7	$210.96	10.775%	$233.6909	$233.69	$233.70	$233.70
7 purchase totals =	$668.70		$733.4912	$733.49	$733.50	$733.60