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	$90.87	4.144%	$94.6357	$94.64	$94.65	$94.60
Purchase #2	$150.25	11.856%	$168.0636	$168.06	$168.05	$168.10
Purchase #3	$121.29	5.451%	$127.9015	$127.90	$127.90	$127.90
Purchase #4	$122.74	9.135%	$133.9523	$133.95	$133.95	$134.00
Purchase #5	$246.76	11.495%	$275.1251	$275.13	$275.15	$275.10
Purchase #6	$102.64	12.334%	$115.2996	$115.30	$115.30	$115.30
Purchase #7	$55.45	10.118%	$61.0604	$61.06	$61.05	$61.10
7 purchase totals =	$890.00		$976.0382	$976.04	$976.05	$976.10