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	$86.56	11.235%	$96.285	$96.29	$96.30	$96.30
Purchase #2	$84.86	6.617%	$90.4752	$90.48	$90.50	$90.50
Purchase #3	$237.47	7.268%	$254.7293	$254.73	$254.75	$254.70
Purchase #4	$103.84	12.207%	$116.5157	$116.52	$116.50	$116.50
Purchase #5	$95.72	7.436%	$102.8377	$102.84	$102.85	$102.80
Purchase #6	$186.92	4.579%	$195.4791	$195.48	$195.50	$195.50
Purchase #7	$104.82	9.322%	$114.5913	$114.59	$114.60	$114.60
7 purchase totals =	$900.19		$970.9133	$970.93	$971.00	$970.90