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	$241.48	10.497%	$266.8282	$266.83	$266.85	$266.80
Purchase #2	$24.40	13.809%	$27.7694	$27.77	$27.75	$27.80
Purchase #3	$101.44	10.804%	$112.3996	$112.40	$112.40	$112.40
Purchase #4	$123.51	3.295%	$127.5797	$127.58	$127.60	$127.60
Purchase #5	$110.43	5.533%	$116.5401	$116.54	$116.55	$116.50
Purchase #6	$241.68	4.377%	$252.2583	$252.26	$252.25	$252.30
Purchase #7	$167.71	6.797%	$179.1092	$179.11	$179.10	$179.10
7 purchase totals =	$1,010.65		$1,082.4845	$1,082.49	$1,082.50	$1,082.50