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	$53.43	11.420%	$59.5317	$59.53	$59.55	$59.50
Purchase #2	$51.90	12.170%	$58.2162	$58.22	$58.20	$58.20
Purchase #3	$51.80	4.680%	$54.2242	$54.22	$54.20	$54.20
Purchase #4	$15.79	5.398%	$16.6423	$16.64	$16.65	$16.60
Purchase #5	$174.49	12.561%	$196.4077	$196.41	$196.40	$196.40
Purchase #6	$95.25	8.673%	$103.511	$103.51	$103.50	$103.50
Purchase #7	$11.49	12.269%	$12.8997	$12.90	$12.90	$12.90
7 purchase totals =	$454.15		$501.4328	$501.43	$501.40	$501.30