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	$132.77	13.284%	$150.4072	$150.41	$150.40	$150.40
Purchase #2	$16.43	8.145%	$17.7682	$17.77	$17.75	$17.80
Purchase #3	$153.93	5.547%	$162.4685	$162.47	$162.45	$162.50
Purchase #4	$244.77	10.332%	$270.0596	$270.06	$270.05	$270.10
Purchase #5	$137.93	3.378%	$142.5893	$142.59	$142.60	$142.60
Purchase #6	$202.51	9.742%	$222.2385	$222.24	$222.25	$222.20
Purchase #7	$127.88	5.469%	$134.8738	$134.87	$134.85	$134.90
7 purchase totals =	$1,016.22		$1,100.4051	$1,100.41	$1,100.35	$1,100.50