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	$176.94	11.136%	$196.644	$196.64	$196.65	$196.60
Purchase #2	$121.68	3.217%	$125.5944	$125.59	$125.60	$125.60
Purchase #3	$38.99	4.595%	$40.7816	$40.78	$40.80	$40.80
Purchase #4	$113.43	7.722%	$122.1891	$122.19	$122.20	$122.20
Purchase #5	$59.26	3.795%	$61.5089	$61.51	$61.50	$61.50
Purchase #6	$176.49	12.653%	$198.8213	$198.82	$198.80	$198.80
Purchase #7	$242.32	5.559%	$255.7906	$255.79	$255.80	$255.80
7 purchase totals =	$929.11		$1,001.3299	$1,001.32	$1,001.35	$1,001.30