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	$13.66	3.532%	$14.1425	$14.14	$14.15	$14.10
Purchase #2	$200.32	12.459%	$225.2779	$225.28	$225.30	$225.30
Purchase #3	$89.83	11.314%	$99.9934	$99.99	$100.00	$100.00
Purchase #4	$52.60	3.456%	$54.4179	$54.42	$54.40	$54.40
Purchase #5	$29.53	12.408%	$33.1941	$33.19	$33.20	$33.20
Purchase #6	$130.92	9.592%	$143.4778	$143.48	$143.50	$143.50
Purchase #7	$108.50	5.558%	$114.5304	$114.53	$114.55	$114.50
7 purchase totals =	$625.36		$685.0340	$685.03	$685.10	$685.00