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	$236.89	13.169%	$268.086	$268.09	$268.10	$268.10
Purchase #2	$110.74	5.500%	$116.8307	$116.83	$116.85	$116.80
Purchase #3	$151.50	4.861%	$158.8644	$158.86	$158.85	$158.90
Purchase #4	$29.25	5.599%	$30.8877	$30.89	$30.90	$30.90
Purchase #5	$125.29	11.609%	$139.8349	$139.83	$139.85	$139.80
Purchase #6	$134.96	13.591%	$153.3024	$153.30	$153.30	$153.30
Purchase #7	$140.84	9.610%	$154.3747	$154.37	$154.35	$154.40
7 purchase totals =	$929.47		$1,022.1808	$1,022.17	$1,022.20	$1,022.20