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	$152.87	6.478%	$162.7729	$162.77	$162.75	$162.80
Purchase #2	$121.89	7.649%	$131.2134	$131.21	$131.20	$131.20
Purchase #3	$185.53	10.624%	$205.2407	$205.24	$205.25	$205.20
Purchase #4	$108.40	11.598%	$120.9722	$120.97	$120.95	$121.00
Purchase #5	$11.82	9.491%	$12.9418	$12.94	$12.95	$12.90
Purchase #6	$207.68	4.607%	$217.2478	$217.25	$217.25	$217.20
Purchase #7	$52.33	13.183%	$59.2287	$59.23	$59.25	$59.20
7 purchase totals =	$840.52		$909.6175	$909.61	$909.60	$909.50