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	$147.71	5.212%	$155.4086	$155.41	$155.40	$155.40
Purchase #2	$104.65	6.644%	$111.6029	$111.60	$111.60	$111.60
Purchase #3	$177.95	5.523%	$187.7782	$187.78	$187.80	$187.80
Purchase #4	$112.51	13.266%	$127.4356	$127.44	$127.45	$127.40
Purchase #5	$187.60	9.594%	$205.5983	$205.60	$205.60	$205.60
Purchase #6	$123.70	9.466%	$135.4094	$135.41	$135.40	$135.40
Purchase #7	$18.50	12.406%	$20.7951	$20.80	$20.80	$20.80
7 purchase totals =	$872.62		$944.0281	$944.04	$944.05	$944.00