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	$78.53	4.293%	$81.9013	$81.90	$81.90	$81.90
Purchase #2	$162.29	9.154%	$177.146	$177.15	$177.15	$177.10
Purchase #3	$106.35	4.443%	$111.0751	$111.08	$111.10	$111.10
Purchase #4	$160.82	7.630%	$173.0906	$173.09	$173.10	$173.10
Purchase #5	$228.95	11.642%	$255.6044	$255.60	$255.60	$255.60
Purchase #6	$245.60	8.744%	$267.0753	$267.08	$267.10	$267.10
Purchase #7	$36.33	11.480%	$40.5007	$40.50	$40.50	$40.50
7 purchase totals =	$1,018.87		$1,106.3934	$1,106.40	$1,106.45	$1,106.40