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	$144.47	12.378%	$162.3525	$162.35	$162.35	$162.40
Purchase #2	$10.99	13.707%	$12.4964	$12.50	$12.50	$12.50
Purchase #3	$48.48	6.321%	$51.5444	$51.54	$51.55	$51.50
Purchase #4	$90.77	12.620%	$102.2252	$102.23	$102.25	$102.20
Purchase #5	$143.54	3.264%	$148.2251	$148.23	$148.25	$148.20
Purchase #6	$118.87	7.375%	$127.6367	$127.64	$127.65	$127.60
Purchase #7	$161.35	4.382%	$168.4204	$168.42	$168.40	$168.40
7 purchase totals =	$718.47		$772.9007	$772.91	$772.95	$772.80