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	$68.71	4.615%	$71.881	$71.88	$71.90	$71.90
Purchase #2	$202.35	9.504%	$221.5813	$221.58	$221.60	$221.60
Purchase #3	$178.29	6.500%	$189.8789	$189.88	$189.90	$189.90
Purchase #4	$178.75	3.820%	$185.5783	$185.58	$185.60	$185.60
Purchase #5	$196.86	3.509%	$203.7678	$203.77	$203.75	$203.80
Purchase #6	$65.38	10.725%	$72.392	$72.39	$72.40	$72.40
Purchase #7	$192.68	4.387%	$201.1329	$201.13	$201.15	$201.10
7 purchase totals =	$1,083.02		$1,146.2122	$1,146.21	$1,146.30	$1,146.30