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	$235.42	11.159%	$261.6905	$261.69	$261.70	$261.70
Purchase #2	$172.31	3.578%	$178.4753	$178.48	$178.50	$178.50
Purchase #3	$20.56	4.429%	$21.4706	$21.47	$21.45	$21.50
Purchase #4	$136.44	5.102%	$143.4012	$143.40	$143.40	$143.40
Purchase #5	$172.94	3.609%	$179.1814	$179.18	$179.20	$179.20
Purchase #6	$233.60	12.377%	$262.5127	$262.51	$262.50	$262.50
Purchase #7	$89.64	13.186%	$101.4599	$101.46	$101.45	$101.50
7 purchase totals =	$1,060.91		$1,148.1916	$1,148.19	$1,148.20	$1,148.30