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	$203.68	7.777%	$219.5202	$219.52	$219.50	$219.50
Purchase #2	$113.83	8.487%	$123.4908	$123.49	$123.50	$123.50
Purchase #3	$83.48	7.197%	$89.4881	$89.49	$89.50	$89.50
Purchase #4	$164.51	9.323%	$179.8473	$179.85	$179.85	$179.80
Purchase #5	$69.25	12.387%	$77.828	$77.83	$77.85	$77.80
Purchase #6	$117.52	5.144%	$123.5652	$123.57	$123.55	$123.60
Purchase #7	$45.89	10.292%	$50.613	$50.61	$50.60	$50.60
7 purchase totals =	$798.16		$864.3526	$864.36	$864.35	$864.30