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	$177.30	10.856%	$196.5477	$196.55	$196.55	$196.50
Purchase #2	$230.67	3.411%	$238.5382	$238.54	$238.55	$238.50
Purchase #3	$139.39	7.131%	$149.3299	$149.33	$149.35	$149.30
Purchase #4	$34.98	9.647%	$38.3545	$38.35	$38.35	$38.40
Purchase #5	$54.44	5.607%	$57.4925	$57.49	$57.50	$57.50
Purchase #6	$63.38	5.164%	$66.6529	$66.65	$66.65	$66.70
Purchase #7	$59.99	13.202%	$67.9099	$67.91	$67.90	$67.90
7 purchase totals =	$760.15		$814.8256	$814.82	$814.85	$814.80