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	$146.29	11.255%	$162.7549	$162.75	$162.75	$162.80
Purchase #2	$180.71	8.602%	$196.2547	$196.25	$196.25	$196.30
Purchase #3	$50.48	7.464%	$54.2478	$54.25	$54.25	$54.20
Purchase #4	$108.81	10.362%	$120.0849	$120.08	$120.10	$120.10
Purchase #5	$34.95	6.701%	$37.292	$37.29	$37.30	$37.30
Purchase #6	$158.25	5.224%	$166.517	$166.52	$166.50	$166.50
Purchase #7	$126.63	3.638%	$131.2368	$131.24	$131.25	$131.20
7 purchase totals =	$806.12		$868.3881	$868.38	$868.40	$868.40