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	$147.56	13.814%	$167.9439	$167.94	$167.95	$167.90
Purchase #2	$36.83	4.757%	$38.582	$38.58	$38.60	$38.60
Purchase #3	$154.57	12.387%	$173.7166	$173.72	$173.70	$173.70
Purchase #4	$11.98	7.545%	$12.8839	$12.88	$12.90	$12.90
Purchase #5	$239.30	4.513%	$250.0996	$250.10	$250.10	$250.10
Purchase #6	$122.86	7.186%	$131.6887	$131.69	$131.70	$131.70
Purchase #7	$22.97	11.318%	$25.5697	$25.57	$25.55	$25.60
7 purchase totals =	$736.07		$800.4844	$800.48	$800.50	$800.50