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	$97.41	3.274%	$100.5992	$100.60	$100.60	$100.60
Purchase #2	$169.47	12.622%	$190.8605	$190.86	$190.85	$190.90
Purchase #3	$183.68	13.473%	$208.4272	$208.43	$208.45	$208.40
Purchase #4	$62.61	8.289%	$67.7997	$67.80	$67.80	$67.80
Purchase #5	$189.81	4.351%	$198.0686	$198.07	$198.05	$198.10
Purchase #6	$166.56	6.120%	$176.7535	$176.75	$176.75	$176.80
Purchase #7	$47.98	12.125%	$53.7976	$53.80	$53.80	$53.80
7 purchase totals =	$917.52		$996.3063	$996.31	$996.30	$996.40