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	$160.46	7.557%	$172.586	$172.59	$172.60	$172.60
Purchase #2	$6.47	10.556%	$7.153	$7.15	$7.15	$7.20
Purchase #3	$106.35	6.640%	$113.4116	$113.41	$113.40	$113.40
Purchase #4	$34.25	5.403%	$36.1005	$36.10	$36.10	$36.10
Purchase #5	$136.83	4.610%	$143.1379	$143.14	$143.15	$143.10
Purchase #6	$239.31	7.155%	$256.4326	$256.43	$256.45	$256.40
Purchase #7	$238.47	4.544%	$249.3061	$249.31	$249.30	$249.30
7 purchase totals =	$922.14		$978.1277	$978.13	$978.15	$978.10