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	$107.73	4.771%	$112.8698	$112.87	$112.85	$112.90
Purchase #2	$13.97	8.657%	$15.1794	$15.18	$15.20	$15.20
Purchase #3	$94.50	10.186%	$104.1258	$104.13	$104.15	$104.10
Purchase #4	$53.43	10.753%	$59.1753	$59.18	$59.20	$59.20
Purchase #5	$172.57	6.227%	$183.3159	$183.32	$183.30	$183.30
Purchase #6	$53.80	13.832%	$61.2416	$61.24	$61.25	$61.20
Purchase #7	$47.45	11.390%	$52.8546	$52.85	$52.85	$52.90
7 purchase totals =	$543.45		$588.7624	$588.77	$588.80	$588.80