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	$27.29	5.770%	$28.8646	$28.86	$28.85	$28.90
Purchase #2	$80.84	12.509%	$90.9523	$90.95	$90.95	$91.00
Purchase #3	$138.54	10.773%	$153.4649	$153.46	$153.45	$153.50
Purchase #4	$72.86	7.376%	$78.2342	$78.23	$78.25	$78.20
Purchase #5	$225.46	4.644%	$235.9304	$235.93	$235.95	$235.90
Purchase #6	$110.43	8.525%	$119.8442	$119.84	$119.85	$119.80
Purchase #7	$28.84	7.844%	$31.1022	$31.10	$31.10	$31.10
7 purchase totals =	$684.26		$738.3928	$738.37	$738.40	$738.40