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	$205.72	10.748%	$227.8308	$227.83	$227.85	$227.80
Purchase #2	$158.55	7.731%	$170.8075	$170.81	$170.80	$170.80
Purchase #3	$130.38	6.452%	$138.7921	$138.79	$138.80	$138.80
Purchase #4	$88.93	13.330%	$100.7844	$100.78	$100.80	$100.80
Purchase #5	$159.85	13.461%	$181.3674	$181.37	$181.35	$181.40
Purchase #6	$114.80	11.136%	$127.5841	$127.58	$127.60	$127.60
Purchase #7	$247.46	8.654%	$268.8752	$268.88	$268.90	$268.90
7 purchase totals =	$1,105.69		$1,216.0415	$1,216.04	$1,216.10	$1,216.10