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	$36.76	5.689%	$38.8513	$38.85	$38.85	$38.90
Purchase #2	$95.92	4.614%	$100.3457	$100.35	$100.35	$100.30
Purchase #3	$65.87	10.472%	$72.7679	$72.77	$72.75	$72.80
Purchase #4	$147.49	7.616%	$158.7228	$158.72	$158.70	$158.70
Purchase #5	$59.47	11.237%	$66.1526	$66.15	$66.15	$66.20
Purchase #6	$227.37	10.742%	$251.7941	$251.79	$251.80	$251.80
Purchase #7	$198.60	7.488%	$213.4712	$213.47	$213.45	$213.50
7 purchase totals =	$831.48		$902.1056	$902.10	$902.05	$902.20