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	$246.94	6.749%	$263.606	$263.61	$263.60	$263.60
Purchase #2	$208.64	4.818%	$218.6923	$218.69	$218.70	$218.70
Purchase #3	$133.54	13.617%	$151.7241	$151.72	$151.70	$151.70
Purchase #4	$72.35	5.693%	$76.4689	$76.47	$76.45	$76.50
Purchase #5	$73.48	7.271%	$78.8227	$78.82	$78.80	$78.80
Purchase #6	$119.70	12.568%	$134.7439	$134.74	$134.75	$134.70
Purchase #7	$56.58	4.837%	$59.3168	$59.32	$59.30	$59.30
7 purchase totals =	$911.23		$983.3747	$983.37	$983.30	$983.30