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	$209.39	8.119%	$226.3904	$226.39	$226.40	$226.40
Purchase #2	$44.26	13.807%	$50.371	$50.37	$50.35	$50.40
Purchase #3	$241.27	7.276%	$258.8248	$258.82	$258.80	$258.80
Purchase #4	$125.48	5.852%	$132.8231	$132.82	$132.80	$132.80
Purchase #5	$28.49	7.448%	$30.6119	$30.61	$30.60	$30.60
Purchase #6	$112.94	13.332%	$127.9972	$128.00	$128.00	$128.00
Purchase #7	$196.59	13.382%	$222.8977	$222.90	$222.90	$222.90
7 purchase totals =	$958.42		$1,049.9161	$1,049.91	$1,049.85	$1,049.90