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	$176.99	12.834%	$199.7049	$199.70	$199.70	$199.70
Purchase #2	$44.46	9.673%	$48.7606	$48.76	$48.75	$48.80
Purchase #3	$50.39	8.531%	$54.6888	$54.69	$54.70	$54.70
Purchase #4	$41.89	8.635%	$45.5072	$45.51	$45.50	$45.50
Purchase #5	$38.73	13.211%	$43.8466	$43.85	$43.85	$43.80
Purchase #6	$49.38	3.606%	$51.1606	$51.16	$51.15	$51.20
Purchase #7	$60.60	3.565%	$62.7604	$62.76	$62.75	$62.80
7 purchase totals =	$462.44		$506.4291	$506.43	$506.40	$506.50