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	$163.77	10.723%	$181.3311	$181.33	$181.35	$181.30
Purchase #2	$37.82	3.677%	$39.2106	$39.21	$39.20	$39.20
Purchase #3	$128.81	7.864%	$138.9396	$138.94	$138.95	$138.90
Purchase #4	$149.40	5.823%	$158.0996	$158.10	$158.10	$158.10
Purchase #5	$109.83	8.426%	$119.0843	$119.08	$119.10	$119.10
Purchase #6	$152.59	13.305%	$172.8921	$172.89	$172.90	$172.90
Purchase #7	$46.74	11.835%	$52.2717	$52.27	$52.25	$52.30
7 purchase totals =	$788.96		$861.8290	$861.82	$861.85	$861.80