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	$88.56	13.419%	$100.4439	$100.44	$100.45	$100.40
Purchase #2	$203.76	11.762%	$227.7263	$227.73	$227.75	$227.70
Purchase #3	$177.60	10.616%	$196.454	$196.45	$196.45	$196.50
Purchase #4	$49.87	5.389%	$52.5575	$52.56	$52.55	$52.60
Purchase #5	$67.37	13.561%	$76.506	$76.51	$76.50	$76.50
Purchase #6	$230.30	7.874%	$248.4338	$248.43	$248.45	$248.40
Purchase #7	$174.37	10.690%	$193.0102	$193.01	$193.00	$193.00
7 purchase totals =	$991.83		$1,095.1317	$1,095.13	$1,095.15	$1,095.10