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	$50.39	6.539%	$53.685	$53.69	$53.70	$53.70
Purchase #2	$100.30	5.642%	$105.9589	$105.96	$105.95	$106.00
Purchase #3	$21.97	11.318%	$24.4566	$24.46	$24.45	$24.50
Purchase #4	$208.51	13.242%	$236.1209	$236.12	$236.10	$236.10
Purchase #5	$37.71	4.550%	$39.4258	$39.43	$39.45	$39.40
Purchase #6	$143.92	4.641%	$150.5993	$150.60	$150.60	$150.60
Purchase #7	$100.27	7.685%	$107.9757	$107.98	$108.00	$108.00
7 purchase totals =	$663.07		$718.2222	$718.24	$718.25	$718.30