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	$132.89	11.665%	$148.3916	$148.39	$148.40	$148.40
Purchase #2	$143.79	10.816%	$159.3423	$159.34	$159.35	$159.30
Purchase #3	$134.59	12.457%	$151.3559	$151.36	$151.35	$151.40
Purchase #4	$218.60	13.619%	$248.3711	$248.37	$248.35	$248.40
Purchase #5	$179.70	9.323%	$196.4534	$196.45	$196.45	$196.50
Purchase #6	$161.57	6.756%	$172.4857	$172.49	$172.50	$172.50
Purchase #7	$116.86	4.578%	$122.2099	$122.21	$122.20	$122.20
7 purchase totals =	$1,088.00		$1,198.6099	$1,198.61	$1,198.60	$1,198.70