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	$82.51	3.772%	$85.6223	$85.62	$85.60	$85.60
Purchase #2	$90.46	8.864%	$98.4784	$98.48	$98.50	$98.50
Purchase #3	$133.99	12.393%	$150.5954	$150.60	$150.60	$150.60
Purchase #4	$24.75	9.235%	$27.0357	$27.04	$27.05	$27.00
Purchase #5	$176.74	5.726%	$186.8601	$186.86	$186.85	$186.90
Purchase #6	$242.43	5.150%	$254.9151	$254.92	$254.90	$254.90
Purchase #7	$95.45	8.202%	$103.2788	$103.28	$103.30	$103.30
7 purchase totals =	$846.33		$906.7858	$906.80	$906.80	$906.80