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	$12.64	7.639%	$13.6056	$13.61	$13.60	$13.60
Purchase #2	$45.90	6.108%	$48.7036	$48.70	$48.70	$48.70
Purchase #3	$51.64	6.245%	$54.8649	$54.86	$54.85	$54.90
Purchase #4	$247.99	7.257%	$265.9866	$265.99	$266.00	$266.00
Purchase #5	$32.51	12.555%	$36.5916	$36.59	$36.60	$36.60
Purchase #6	$160.59	8.651%	$174.4826	$174.48	$174.50	$174.50
Purchase #7	$231.37	10.231%	$255.0415	$255.04	$255.05	$255.00
7 purchase totals =	$782.64		$849.2764	$849.27	$849.30	$849.30