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	$59.81	12.720%	$67.4178	$67.42	$67.40	$67.40
Purchase #2	$184.38	5.321%	$194.1909	$194.19	$194.20	$194.20
Purchase #3	$10.74	13.594%	$12.2	$12.20	$12.20	$12.20
Purchase #4	$36.60	4.787%	$38.352	$38.35	$38.35	$38.40
Purchase #5	$206.65	7.854%	$222.8803	$222.88	$222.90	$222.90
Purchase #6	$77.52	11.282%	$86.2658	$86.27	$86.25	$86.30
Purchase #7	$172.43	6.219%	$183.1534	$183.15	$183.15	$183.20
7 purchase totals =	$748.13		$804.4602	$804.46	$804.45	$804.60