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	$49.94	9.412%	$54.6404	$54.64	$54.65	$54.60
Purchase #2	$37.72	12.382%	$42.3905	$42.39	$42.40	$42.40
Purchase #3	$154.34	9.322%	$168.7276	$168.73	$168.75	$168.70
Purchase #4	$122.28	5.383%	$128.8623	$128.86	$128.85	$128.90
Purchase #5	$218.70	5.594%	$230.9341	$230.93	$230.95	$230.90
Purchase #6	$250.39	8.404%	$271.4328	$271.43	$271.45	$271.40
Purchase #7	$184.92	6.432%	$196.8141	$196.81	$196.80	$196.80
7 purchase totals =	$1,018.29		$1,093.8018	$1,093.79	$1,093.85	$1,093.70