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	$219.89	4.726%	$230.282	$230.28	$230.30	$230.30
Purchase #2	$246.82	3.759%	$256.098	$256.10	$256.10	$256.10
Purchase #3	$34.72	13.575%	$39.4332	$39.43	$39.45	$39.40
Purchase #4	$27.71	12.664%	$31.2192	$31.22	$31.20	$31.20
Purchase #5	$234.43	10.434%	$258.8904	$258.89	$258.90	$258.90
Purchase #6	$184.63	6.557%	$196.7362	$196.74	$196.75	$196.70
Purchase #7	$27.35	9.337%	$29.9037	$29.90	$29.90	$29.90
7 purchase totals =	$975.55		$1,042.5627	$1,042.56	$1,042.60	$1,042.50