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	$247.66	9.642%	$271.5394	$271.54	$271.55	$271.50
Purchase #2	$132.62	7.678%	$142.8026	$142.80	$142.80	$142.80
Purchase #3	$54.56	8.693%	$59.3029	$59.30	$59.30	$59.30
Purchase #4	$141.31	8.608%	$153.474	$153.47	$153.45	$153.50
Purchase #5	$195.32	4.205%	$203.5332	$203.53	$203.55	$203.50
Purchase #6	$37.47	10.529%	$41.4152	$41.42	$41.40	$41.40
Purchase #7	$56.31	7.577%	$60.5766	$60.58	$60.60	$60.60
7 purchase totals =	$865.25		$932.6439	$932.64	$932.65	$932.60