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	$133.53	7.533%	$143.5888	$143.59	$143.60	$143.60
Purchase #2	$78.97	8.723%	$85.8586	$85.86	$85.85	$85.90
Purchase #3	$21.75	8.684%	$23.6388	$23.64	$23.65	$23.60
Purchase #4	$235.66	10.725%	$260.9345	$260.93	$260.95	$260.90
Purchase #5	$188.44	13.190%	$213.2952	$213.30	$213.30	$213.30
Purchase #6	$153.56	3.215%	$158.497	$158.50	$158.50	$158.50
Purchase #7	$150.27	12.127%	$168.4932	$168.49	$168.50	$168.50
7 purchase totals =	$962.18		$1,054.3061	$1,054.31	$1,054.35	$1,054.30