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	$159.42	12.676%	$179.6281	$179.63	$179.65	$179.60
Purchase #2	$37.89	13.435%	$42.9805	$42.98	$43.00	$43.00
Purchase #3	$40.28	13.699%	$45.798	$45.80	$45.80	$45.80
Purchase #4	$34.69	10.276%	$38.2547	$38.25	$38.25	$38.30
Purchase #5	$147.80	12.322%	$166.0119	$166.01	$166.00	$166.00
Purchase #6	$50.95	5.856%	$53.9336	$53.93	$53.95	$53.90
Purchase #7	$238.87	3.632%	$247.5458	$247.55	$247.55	$247.50
7 purchase totals =	$709.90		$774.1526	$774.15	$774.20	$774.10