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	$208.44	6.523%	$222.0365	$222.04	$222.05	$222.00
Purchase #2	$197.47	8.600%	$214.4524	$214.45	$214.45	$214.50
Purchase #3	$243.76	9.735%	$267.49	$267.49	$267.50	$267.50
Purchase #4	$71.57	10.111%	$78.8064	$78.81	$78.80	$78.80
Purchase #5	$150.79	5.355%	$158.8648	$158.86	$158.85	$158.90
Purchase #6	$211.45	7.578%	$227.4737	$227.47	$227.45	$227.50
Purchase #7	$38.93	9.733%	$42.7191	$42.72	$42.70	$42.70
7 purchase totals =	$1,122.41		$1,211.8429	$1,211.84	$1,211.80	$1,211.90