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	$116.89	13.557%	$132.7368	$132.74	$132.75	$132.70
Purchase #2	$187.96	10.348%	$207.4101	$207.41	$207.40	$207.40
Purchase #3	$93.85	5.309%	$98.8325	$98.83	$98.85	$98.80
Purchase #4	$14.25	9.753%	$15.6398	$15.64	$15.65	$15.60
Purchase #5	$216.69	12.762%	$244.344	$244.34	$244.35	$244.30
Purchase #6	$127.67	4.532%	$133.456	$133.46	$133.45	$133.50
Purchase #7	$54.86	8.392%	$59.4639	$59.46	$59.45	$59.50
7 purchase totals =	$812.17		$891.8831	$891.88	$891.90	$891.80