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	$216.85	9.671%	$237.8216	$237.82	$237.80	$237.80
Purchase #2	$115.77	10.406%	$127.817	$127.82	$127.80	$127.80
Purchase #3	$119.94	13.151%	$135.7133	$135.71	$135.70	$135.70
Purchase #4	$241.78	6.492%	$257.4764	$257.48	$257.50	$257.50
Purchase #5	$69.35	10.443%	$76.5922	$76.59	$76.60	$76.60
Purchase #6	$62.44	3.756%	$64.7852	$64.79	$64.80	$64.80
Purchase #7	$182.67	7.750%	$196.8269	$196.83	$196.85	$196.80
7 purchase totals =	$1,008.80		$1,097.0326	$1,097.04	$1,097.05	$1,097.00