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	$132.87	13.549%	$150.8726	$150.87	$150.85	$150.90
Purchase #2	$30.95	13.105%	$35.006	$35.01	$35.00	$35.00
Purchase #3	$183.65	10.518%	$202.9663	$202.97	$202.95	$203.00
Purchase #4	$82.40	8.403%	$89.3241	$89.32	$89.30	$89.30
Purchase #5	$196.73	5.184%	$206.9285	$206.93	$206.95	$206.90
Purchase #6	$60.27	9.390%	$65.9294	$65.93	$65.95	$65.90
Purchase #7	$132.33	9.143%	$144.4289	$144.43	$144.45	$144.40
7 purchase totals =	$819.20		$895.4558	$895.46	$895.45	$895.40