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	$140.30	4.602%	$146.7566	$146.76	$146.75	$146.80
Purchase #2	$249.76	5.816%	$264.286	$264.29	$264.30	$264.30
Purchase #3	$238.55	11.126%	$265.0911	$265.09	$265.10	$265.10
Purchase #4	$57.57	11.338%	$64.0973	$64.10	$64.10	$64.10
Purchase #5	$203.84	9.505%	$223.215	$223.22	$223.20	$223.20
Purchase #6	$122.97	3.761%	$127.5949	$127.59	$127.60	$127.60
Purchase #7	$187.71	5.225%	$197.5178	$197.52	$197.50	$197.50
7 purchase totals =	$1,200.70		$1,288.5587	$1,288.57	$1,288.55	$1,288.60