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	$149.68	8.643%	$162.6168	$162.62	$162.60	$162.60
Purchase #2	$178.42	5.727%	$188.6381	$188.64	$188.65	$188.60
Purchase #3	$136.94	5.612%	$144.6251	$144.63	$144.65	$144.60
Purchase #4	$106.55	10.400%	$117.6312	$117.63	$117.65	$117.60
Purchase #5	$81.43	10.478%	$89.9622	$89.96	$89.95	$90.00
Purchase #6	$45.38	3.443%	$46.9424	$46.94	$46.95	$46.90
Purchase #7	$143.93	8.820%	$156.6246	$156.62	$156.60	$156.60
7 purchase totals =	$842.33		$907.0404	$907.04	$907.05	$906.90