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	$74.56	11.230%	$82.9331	$82.93	$82.95	$82.90
Purchase #2	$182.84	7.713%	$196.9424	$196.94	$196.95	$196.90
Purchase #3	$66.61	9.483%	$72.9266	$72.93	$72.95	$72.90
Purchase #4	$229.81	4.693%	$240.595	$240.60	$240.60	$240.60
Purchase #5	$172.25	5.563%	$181.8323	$181.83	$181.85	$181.80
Purchase #6	$128.59	10.327%	$141.8695	$141.87	$141.85	$141.90
Purchase #7	$193.57	5.555%	$204.3228	$204.32	$204.30	$204.30
7 purchase totals =	$1,048.23		$1,121.4217	$1,121.42	$1,121.45	$1,121.30