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	$234.74	9.446%	$256.9135	$256.91	$256.90	$256.90
Purchase #2	$211.61	9.579%	$231.8801	$231.88	$231.90	$231.90
Purchase #3	$40.56	7.848%	$43.7431	$43.74	$43.75	$43.70
Purchase #4	$116.96	9.161%	$127.6747	$127.67	$127.65	$127.70
Purchase #5	$25.57	13.109%	$28.922	$28.92	$28.90	$28.90
Purchase #6	$208.51	5.223%	$219.4005	$219.40	$219.40	$219.40
Purchase #7	$137.99	11.163%	$153.3938	$153.39	$153.40	$153.40
7 purchase totals =	$975.94		$1,061.9277	$1,061.91	$1,061.90	$1,061.90