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	$222.50	7.420%	$239.0095	$239.01	$239.00	$239.00
Purchase #2	$168.50	3.817%	$174.9316	$174.93	$174.95	$174.90
Purchase #3	$184.94	3.813%	$191.9918	$191.99	$192.00	$192.00
Purchase #4	$205.78	13.309%	$233.1673	$233.17	$233.15	$233.20
Purchase #5	$103.69	8.371%	$112.3699	$112.37	$112.35	$112.40
Purchase #6	$112.54	13.249%	$127.4504	$127.45	$127.45	$127.50
Purchase #7	$10.51	13.481%	$11.9269	$11.93	$11.95	$11.90
7 purchase totals =	$1,008.46		$1,090.8474	$1,090.85	$1,090.85	$1,090.90