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	$63.50	7.872%	$68.4987	$68.50	$68.50	$68.50
Purchase #2	$95.80	3.791%	$99.4318	$99.43	$99.45	$99.40
Purchase #3	$175.70	3.358%	$181.6	$181.60	$181.60	$181.60
Purchase #4	$110.85	3.382%	$114.5989	$114.60	$114.60	$114.60
Purchase #5	$114.80	9.607%	$125.8288	$125.83	$125.85	$125.80
Purchase #6	$127.47	11.861%	$142.5892	$142.59	$142.60	$142.60
Purchase #7	$25.94	8.103%	$28.0419	$28.04	$28.05	$28.00
7 purchase totals =	$714.06		$760.5893	$760.59	$760.65	$760.50