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	$150.33	13.706%	$170.9342	$170.93	$170.95	$170.90
Purchase #2	$133.92	7.158%	$143.506	$143.51	$143.50	$143.50
Purchase #3	$51.82	5.154%	$54.4908	$54.49	$54.50	$54.50
Purchase #4	$214.96	3.105%	$221.6345	$221.63	$221.65	$221.60
Purchase #5	$123.34	7.411%	$132.4807	$132.48	$132.50	$132.50
Purchase #6	$129.41	11.381%	$144.1382	$144.14	$144.15	$144.10
Purchase #7	$131.81	6.711%	$140.6558	$140.66	$140.65	$140.70
7 purchase totals =	$935.59		$1,007.8402	$1,007.84	$1,007.90	$1,007.80