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	$231.55	10.768%	$256.4833	$256.48	$256.50	$256.50
Purchase #2	$109.80	6.250%	$116.6625	$116.66	$116.65	$116.70
Purchase #3	$241.90	12.511%	$272.1641	$272.16	$272.15	$272.20
Purchase #4	$65.25	10.562%	$72.1417	$72.14	$72.15	$72.10
Purchase #5	$83.34	8.567%	$90.4797	$90.48	$90.50	$90.50
Purchase #6	$54.88	9.352%	$60.0124	$60.01	$60.00	$60.00
Purchase #7	$205.51	10.325%	$226.7289	$226.73	$226.75	$226.70
7 purchase totals =	$992.23		$1,094.6726	$1,094.66	$1,094.70	$1,094.70