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	$161.98	11.173%	$180.078	$180.08	$180.10	$180.10
Purchase #2	$66.38	6.161%	$70.4697	$70.47	$70.45	$70.50
Purchase #3	$67.79	12.660%	$76.3722	$76.37	$76.35	$76.40
Purchase #4	$225.96	13.256%	$255.9133	$255.91	$255.90	$255.90
Purchase #5	$88.94	6.397%	$94.6295	$94.63	$94.65	$94.60
Purchase #6	$180.94	8.543%	$196.3977	$196.40	$196.40	$196.40
Purchase #7	$243.28	9.176%	$265.6034	$265.60	$265.60	$265.60
7 purchase totals =	$1,035.27		$1,139.4638	$1,139.46	$1,139.45	$1,139.50