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	$87.56	11.170%	$97.3405	$97.34	$97.35	$97.30
Purchase #2	$226.46	11.523%	$252.555	$252.56	$252.55	$252.60
Purchase #3	$241.72	7.270%	$259.293	$259.29	$259.30	$259.30
Purchase #4	$24.30	5.485%	$25.6329	$25.63	$25.65	$25.60
Purchase #5	$36.75	10.493%	$40.6062	$40.61	$40.60	$40.60
Purchase #6	$152.56	9.673%	$167.3171	$167.32	$167.30	$167.30
Purchase #7	$237.81	7.571%	$255.8146	$255.81	$255.80	$255.80
7 purchase totals =	$1,007.16		$1,098.5593	$1,098.56	$1,098.55	$1,098.50