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	$21.37	4.725%	$22.3797	$22.38	$22.40	$22.40
Purchase #2	$55.98	3.358%	$57.8598	$57.86	$57.85	$57.90
Purchase #3	$70.52	5.529%	$74.4191	$74.42	$74.40	$74.40
Purchase #4	$99.50	3.287%	$102.7706	$102.77	$102.75	$102.80
Purchase #5	$84.72	5.104%	$89.0441	$89.04	$89.05	$89.00
Purchase #6	$152.97	13.475%	$173.5827	$173.58	$173.60	$173.60
Purchase #7	$144.59	7.111%	$154.8718	$154.87	$154.85	$154.90
7 purchase totals =	$629.65		$674.9278	$674.92	$674.90	$675.00