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	$135.44	11.868%	$151.514	$151.51	$151.50	$151.50
Purchase #2	$210.37	5.495%	$221.9298	$221.93	$221.95	$221.90
Purchase #3	$34.25	11.810%	$38.2949	$38.29	$38.30	$38.30
Purchase #4	$127.85	6.854%	$136.6128	$136.61	$136.60	$136.60
Purchase #5	$118.43	6.583%	$126.2262	$126.23	$126.25	$126.20
Purchase #6	$214.95	11.402%	$239.4586	$239.46	$239.45	$239.50
Purchase #7	$104.54	11.384%	$116.4408	$116.44	$116.45	$116.40
7 purchase totals =	$945.83		$1,030.4771	$1,030.47	$1,030.50	$1,030.40