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	$172.78	7.162%	$185.1545	$185.15	$185.15	$185.20
Purchase #2	$58.82	7.323%	$63.1274	$63.13	$63.15	$63.10
Purchase #3	$113.37	6.210%	$120.4103	$120.41	$120.40	$120.40
Purchase #4	$54.33	9.231%	$59.3452	$59.35	$59.35	$59.30
Purchase #5	$9.85	7.393%	$10.5782	$10.58	$10.60	$10.60
Purchase #6	$132.69	7.855%	$143.1128	$143.11	$143.10	$143.10
Purchase #7	$237.25	6.530%	$252.7424	$252.74	$252.75	$252.70
7 purchase totals =	$779.09		$834.4708	$834.47	$834.50	$834.40