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	$145.35	10.824%	$161.0827	$161.08	$161.10	$161.10
Purchase #2	$105.31	10.684%	$116.5613	$116.56	$116.55	$116.60
Purchase #3	$143.59	6.806%	$153.3627	$153.36	$153.35	$153.40
Purchase #4	$52.87	9.702%	$57.9994	$58.00	$58.00	$58.00
Purchase #5	$75.38	3.808%	$78.2505	$78.25	$78.25	$78.30
Purchase #6	$177.70	12.768%	$200.3887	$200.39	$200.40	$200.40
Purchase #7	$222.56	5.627%	$235.0835	$235.08	$235.10	$235.10
7 purchase totals =	$922.76		$1,002.7288	$1,002.72	$1,002.75	$1,002.90