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	$204.96	9.225%	$223.8676	$223.87	$223.85	$223.90
Purchase #2	$132.52	4.847%	$138.9432	$138.94	$138.95	$138.90
Purchase #3	$47.58	11.133%	$52.8771	$52.88	$52.90	$52.90
Purchase #4	$80.81	7.683%	$87.0186	$87.02	$87.00	$87.00
Purchase #5	$199.88	13.243%	$226.3501	$226.35	$226.35	$226.40
Purchase #6	$117.74	8.360%	$127.5831	$127.58	$127.60	$127.60
Purchase #7	$201.98	10.644%	$223.4788	$223.48	$223.50	$223.50
7 purchase totals =	$985.47		$1,080.1185	$1,080.12	$1,080.15	$1,080.20