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	$46.80	8.466%	$50.7621	$50.76	$50.75	$50.80
Purchase #2	$92.81	13.405%	$105.2512	$105.25	$105.25	$105.30
Purchase #3	$38.82	7.451%	$41.7125	$41.71	$41.70	$41.70
Purchase #4	$61.72	6.703%	$65.8571	$65.86	$65.85	$65.90
Purchase #5	$176.80	10.720%	$195.753	$195.75	$195.75	$195.80
Purchase #6	$131.26	8.603%	$142.5523	$142.55	$142.55	$142.60
Purchase #7	$60.97	7.805%	$65.7287	$65.73	$65.75	$65.70
7 purchase totals =	$609.18		$667.6169	$667.61	$667.60	$667.80