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	$56.66	5.773%	$59.931	$59.93	$59.95	$59.90
Purchase #2	$238.71	9.520%	$261.4352	$261.44	$261.45	$261.40
Purchase #3	$62.58	12.264%	$70.2548	$70.25	$70.25	$70.30
Purchase #4	$230.91	3.152%	$238.1883	$238.19	$238.20	$238.20
Purchase #5	$15.89	10.793%	$17.605	$17.61	$17.60	$17.60
Purchase #6	$237.91	13.685%	$270.468	$270.47	$270.45	$270.50
Purchase #7	$114.88	11.417%	$127.9958	$128.00	$128.00	$128.00
7 purchase totals =	$957.54		$1,045.8781	$1,045.89	$1,045.90	$1,045.90