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	$141.50	10.370%	$156.1736	$156.17	$156.15	$156.20
Purchase #2	$204.44	11.155%	$227.2453	$227.25	$227.25	$227.20
Purchase #3	$10.66	13.340%	$12.082	$12.08	$12.10	$12.10
Purchase #4	$232.91	7.171%	$249.612	$249.61	$249.60	$249.60
Purchase #5	$84.68	13.275%	$95.9213	$95.92	$95.90	$95.90
Purchase #6	$249.25	5.334%	$262.545	$262.55	$262.55	$262.50
Purchase #7	$11.54	11.159%	$12.8277	$12.83	$12.85	$12.80
7 purchase totals =	$934.98		$1,016.4069	$1,016.41	$1,016.40	$1,016.30