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	$112.51	9.643%	$123.3593	$123.36	$123.35	$123.40
Purchase #2	$195.63	5.655%	$206.6929	$206.69	$206.70	$206.70
Purchase #3	$31.90	4.857%	$33.4494	$33.45	$33.45	$33.40
Purchase #4	$40.59	9.418%	$44.4128	$44.41	$44.40	$44.40
Purchase #5	$92.73	12.361%	$104.1924	$104.19	$104.20	$104.20
Purchase #6	$152.56	5.293%	$160.635	$160.64	$160.65	$160.60
Purchase #7	$57.58	13.795%	$65.5232	$65.52	$65.50	$65.50
7 purchase totals =	$683.50		$738.2650	$738.26	$738.25	$738.20