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	$94.98	5.772%	$100.4622	$100.46	$100.45	$100.50
Purchase #2	$58.47	8.419%	$63.3926	$63.39	$63.40	$63.40
Purchase #3	$33.63	13.157%	$38.0547	$38.05	$38.05	$38.10
Purchase #4	$90.45	4.586%	$94.598	$94.60	$94.60	$94.60
Purchase #5	$66.27	13.183%	$75.0064	$75.01	$75.00	$75.00
Purchase #6	$180.42	4.336%	$188.243	$188.24	$188.25	$188.20
Purchase #7	$37.68	6.527%	$40.1394	$40.14	$40.15	$40.10
7 purchase totals =	$561.90		$599.8963	$599.89	$599.90	$599.90