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	$212.52	3.282%	$219.4949	$219.49	$219.50	$219.50
Purchase #2	$51.95	4.675%	$54.3787	$54.38	$54.40	$54.40
Purchase #3	$95.36	10.657%	$105.5225	$105.52	$105.50	$105.50
Purchase #4	$157.36	12.105%	$176.4084	$176.41	$176.40	$176.40
Purchase #5	$144.71	13.510%	$164.2603	$164.26	$164.25	$164.30
Purchase #6	$107.72	5.400%	$113.5369	$113.54	$113.55	$113.50
Purchase #7	$236.44	5.809%	$250.1748	$250.17	$250.15	$250.20
7 purchase totals =	$1,006.06		$1,083.7765	$1,083.77	$1,083.75	$1,083.80