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	$76.91	13.613%	$87.3798	$87.38	$87.40	$87.40
Purchase #2	$57.94	4.377%	$60.476	$60.48	$60.50	$60.50
Purchase #3	$53.54	11.345%	$59.6141	$59.61	$59.60	$59.60
Purchase #4	$84.64	6.476%	$90.1213	$90.12	$90.10	$90.10
Purchase #5	$161.76	5.410%	$170.5112	$170.51	$170.50	$170.50
Purchase #6	$141.89	8.854%	$154.4529	$154.45	$154.45	$154.50
Purchase #7	$219.59	9.272%	$239.9504	$239.95	$239.95	$240.00
7 purchase totals =	$796.27		$862.5057	$862.50	$862.50	$862.60