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	$106.95	6.164%	$113.5424	$113.54	$113.55	$113.50
Purchase #2	$51.75	4.726%	$54.1957	$54.20	$54.20	$54.20
Purchase #3	$224.36	4.393%	$234.2161	$234.22	$234.20	$234.20
Purchase #4	$181.96	4.761%	$190.6231	$190.62	$190.60	$190.60
Purchase #5	$54.51	5.246%	$57.3696	$57.37	$57.35	$57.40
Purchase #6	$150.29	5.720%	$158.8866	$158.89	$158.90	$158.90
Purchase #7	$137.33	11.846%	$153.5981	$153.60	$153.60	$153.60
7 purchase totals =	$907.15		$962.4316	$962.44	$962.40	$962.40