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	$234.78	8.549%	$254.8513	$254.85	$254.85	$254.90
Purchase #2	$209.54	13.747%	$238.3455	$238.35	$238.35	$238.30
Purchase #3	$21.61	3.365%	$22.3372	$22.34	$22.35	$22.30
Purchase #4	$164.43	3.124%	$169.5668	$169.57	$169.55	$169.60
Purchase #5	$143.53	13.267%	$162.5721	$162.57	$162.55	$162.60
Purchase #6	$40.54	3.111%	$41.8012	$41.80	$41.80	$41.80
Purchase #7	$70.84	10.392%	$78.2017	$78.20	$78.20	$78.20
7 purchase totals =	$885.27		$967.6758	$967.68	$967.65	$967.70