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	$95.69	11.409%	$106.6073	$106.61	$106.60	$106.60
Purchase #2	$233.87	9.714%	$256.5881	$256.59	$256.60	$256.60
Purchase #3	$196.44	4.700%	$205.6727	$205.67	$205.65	$205.70
Purchase #4	$6.47	13.755%	$7.3599	$7.36	$7.35	$7.40
Purchase #5	$247.28	3.236%	$255.282	$255.28	$255.30	$255.30
Purchase #6	$121.47	7.636%	$130.7454	$130.75	$130.75	$130.70
Purchase #7	$46.71	11.793%	$52.2185	$52.22	$52.20	$52.20
7 purchase totals =	$947.93		$1,014.4739	$1,014.48	$1,014.45	$1,014.50