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	$220.40	6.798%	$235.3828	$235.38	$235.40	$235.40
Purchase #2	$108.50	3.658%	$112.4689	$112.47	$112.45	$112.50
Purchase #3	$171.28	9.664%	$187.8325	$187.83	$187.85	$187.80
Purchase #4	$208.50	5.717%	$220.4199	$220.42	$220.40	$220.40
Purchase #5	$65.40	3.689%	$67.8126	$67.81	$67.80	$67.80
Purchase #6	$114.39	13.857%	$130.241	$130.24	$130.25	$130.20
Purchase #7	$158.45	6.566%	$168.8538	$168.85	$168.85	$168.90
7 purchase totals =	$1,046.92		$1,123.0115	$1,123.00	$1,123.00	$1,123.00