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	$73.51	12.159%	$82.4481	$82.45	$82.45	$82.40
Purchase #2	$66.88	6.730%	$71.381	$71.38	$71.40	$71.40
Purchase #3	$141.54	9.177%	$154.5291	$154.53	$154.55	$154.50
Purchase #4	$151.42	10.739%	$167.681	$167.68	$167.70	$167.70
Purchase #5	$49.62	10.519%	$54.8395	$54.84	$54.85	$54.80
Purchase #6	$98.49	5.455%	$103.8626	$103.86	$103.85	$103.90
Purchase #7	$107.34	5.812%	$113.5786	$113.58	$113.60	$113.60
7 purchase totals =	$688.80		$748.3199	$748.32	$748.40	$748.30