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	$6.67	10.520%	$7.3717	$7.37	$7.35	$7.40
Purchase #2	$59.27	13.794%	$67.4457	$67.45	$67.45	$67.40
Purchase #3	$71.69	3.571%	$74.25	$74.25	$74.25	$74.30
Purchase #4	$44.53	11.146%	$49.4933	$49.49	$49.50	$49.50
Purchase #5	$10.96	5.575%	$11.571	$11.57	$11.55	$11.60
Purchase #6	$71.70	8.231%	$77.6016	$77.60	$77.60	$77.60
Purchase #7	$105.88	9.848%	$116.3071	$116.31	$116.30	$116.30
7 purchase totals =	$370.70		$404.0404	$404.04	$404.00	$404.10