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	$215.99	13.395%	$244.9219	$244.92	$244.90	$244.90
Purchase #2	$203.83	10.503%	$225.2383	$225.24	$225.25	$225.20
Purchase #3	$159.39	4.240%	$166.1481	$166.15	$166.15	$166.10
Purchase #4	$118.58	11.288%	$131.9653	$131.97	$131.95	$132.00
Purchase #5	$131.29	10.552%	$145.1437	$145.14	$145.15	$145.10
Purchase #6	$101.68	5.510%	$107.2826	$107.28	$107.30	$107.30
Purchase #7	$95.80	7.788%	$103.2609	$103.26	$103.25	$103.30
7 purchase totals =	$1,026.56		$1,123.9608	$1,123.96	$1,123.95	$1,123.90