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	$95.28	5.750%	$100.7586	$100.76	$100.75	$100.80
Purchase #2	$158.76	8.457%	$172.1863	$172.19	$172.20	$172.20
Purchase #3	$216.29	8.445%	$234.5557	$234.56	$234.55	$234.60
Purchase #4	$30.33	13.325%	$34.3715	$34.37	$34.35	$34.40
Purchase #5	$66.55	6.807%	$71.0801	$71.08	$71.10	$71.10
Purchase #6	$36.39	11.548%	$40.5923	$40.59	$40.60	$40.60
Purchase #7	$64.65	9.822%	$70.9999	$71.00	$71.00	$71.00
7 purchase totals =	$668.25		$724.5444	$724.55	$724.55	$724.70