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	$133.97	12.163%	$150.2648	$150.26	$150.25	$150.30
Purchase #2	$62.62	8.836%	$68.1531	$68.15	$68.15	$68.20
Purchase #3	$55.31	6.817%	$59.0805	$59.08	$59.10	$59.10
Purchase #4	$66.51	12.549%	$74.8563	$74.86	$74.85	$74.90
Purchase #5	$146.45	4.403%	$152.8982	$152.90	$152.90	$152.90
Purchase #6	$158.76	8.446%	$172.1689	$172.17	$172.15	$172.20
Purchase #7	$107.27	13.554%	$121.8094	$121.81	$121.80	$121.80
7 purchase totals =	$730.89		$799.2312	$799.23	$799.20	$799.40