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	$156.67	5.275%	$164.9343	$164.93	$164.95	$164.90
Purchase #2	$244.32	11.175%	$271.6228	$271.62	$271.60	$271.60
Purchase #3	$54.87	13.269%	$62.1507	$62.15	$62.15	$62.20
Purchase #4	$153.78	10.851%	$170.4667	$170.47	$170.45	$170.50
Purchase #5	$87.87	8.440%	$95.2862	$95.29	$95.30	$95.30
Purchase #6	$125.77	4.705%	$131.6875	$131.69	$131.70	$131.70
Purchase #7	$69.42	13.693%	$78.9257	$78.93	$78.95	$78.90
7 purchase totals =	$892.70		$975.0739	$975.08	$975.10	$975.10