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	$47.40	10.595%	$52.422	$52.42	$52.40	$52.40
Purchase #2	$51.39	8.650%	$55.8352	$55.84	$55.85	$55.80
Purchase #3	$220.93	7.641%	$237.8113	$237.81	$237.80	$237.80
Purchase #4	$40.38	11.660%	$45.0883	$45.09	$45.10	$45.10
Purchase #5	$152.67	5.608%	$161.2317	$161.23	$161.25	$161.20
Purchase #6	$173.29	13.206%	$196.1747	$196.17	$196.15	$196.20
Purchase #7	$57.80	11.660%	$64.5395	$64.54	$64.55	$64.50
7 purchase totals =	$743.86		$813.1027	$813.10	$813.10	$813.00