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	$92.76	9.330%	$101.4145	$101.41	$101.40	$101.40
Purchase #2	$229.68	13.824%	$261.431	$261.43	$261.45	$261.40
Purchase #3	$241.76	8.689%	$262.7665	$262.77	$262.75	$262.80
Purchase #4	$95.82	13.388%	$108.6484	$108.65	$108.65	$108.60
Purchase #5	$79.46	12.584%	$89.4592	$89.46	$89.45	$89.50
Purchase #6	$123.64	7.568%	$132.9971	$133.00	$133.00	$133.00
Purchase #7	$134.55	7.124%	$144.1353	$144.14	$144.15	$144.10
7 purchase totals =	$997.67		$1,100.8520	$1,100.86	$1,100.85	$1,100.80