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	$211.99	10.628%	$234.5203	$234.52	$234.50	$234.50
Purchase #2	$45.34	11.433%	$50.5237	$50.52	$50.50	$50.50
Purchase #3	$111.55	6.408%	$118.6981	$118.70	$118.70	$118.70
Purchase #4	$101.88	12.783%	$114.9033	$114.90	$114.90	$114.90
Purchase #5	$196.49	8.846%	$213.8715	$213.87	$213.85	$213.90
Purchase #6	$59.45	13.189%	$67.2909	$67.29	$67.30	$67.30
Purchase #7	$127.95	10.858%	$141.8428	$141.84	$141.85	$141.80
7 purchase totals =	$854.65		$941.6506	$941.64	$941.60	$941.60