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	$87.73	8.845%	$95.4897	$95.49	$95.50	$95.50
Purchase #2	$53.65	7.358%	$57.5976	$57.60	$57.60	$57.60
Purchase #3	$134.32	13.145%	$151.9764	$151.98	$152.00	$152.00
Purchase #4	$250.80	6.744%	$267.714	$267.71	$267.70	$267.70
Purchase #5	$54.72	13.143%	$61.9118	$61.91	$61.90	$61.90
Purchase #6	$142.60	5.855%	$150.9492	$150.95	$150.95	$150.90
Purchase #7	$189.40	12.874%	$213.7834	$213.78	$213.80	$213.80
7 purchase totals =	$913.22		$999.4221	$999.42	$999.45	$999.40