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	$155.91	5.209%	$164.0314	$164.03	$164.05	$164.00
Purchase #2	$101.53	11.208%	$112.9095	$112.91	$112.90	$112.90
Purchase #3	$84.40	7.603%	$90.8169	$90.82	$90.80	$90.80
Purchase #4	$56.90	12.246%	$63.868	$63.87	$63.85	$63.90
Purchase #5	$130.34	10.213%	$143.6516	$143.65	$143.65	$143.70
Purchase #6	$45.67	10.433%	$50.4348	$50.43	$50.45	$50.40
Purchase #7	$147.83	10.148%	$162.8318	$162.83	$162.85	$162.80
7 purchase totals =	$722.58		$788.5440	$788.54	$788.55	$788.50