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	$246.95	3.294%	$255.0845	$255.08	$255.10	$255.10
Purchase #2	$134.30	13.385%	$152.2761	$152.28	$152.30	$152.30
Purchase #3	$198.57	12.668%	$223.7248	$223.72	$223.70	$223.70
Purchase #4	$160.29	4.527%	$167.5463	$167.55	$167.55	$167.50
Purchase #5	$51.81	4.723%	$54.257	$54.26	$54.25	$54.30
Purchase #6	$65.90	12.566%	$74.181	$74.18	$74.20	$74.20
Purchase #7	$199.48	13.491%	$226.3918	$226.39	$226.40	$226.40
7 purchase totals =	$1,057.30		$1,153.4615	$1,153.46	$1,153.50	$1,153.50