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	$29.86	8.225%	$32.316	$32.32	$32.30	$32.30
Purchase #2	$117.29	3.256%	$121.109	$121.11	$121.10	$121.10
Purchase #3	$206.46	7.177%	$221.2776	$221.28	$221.30	$221.30
Purchase #4	$92.39	10.420%	$102.017	$102.02	$102.00	$102.00
Purchase #5	$124.40	3.478%	$128.7266	$128.73	$128.75	$128.70
Purchase #6	$151.85	11.255%	$168.9407	$168.94	$168.95	$168.90
Purchase #7	$226.84	6.624%	$241.8659	$241.87	$241.85	$241.90
7 purchase totals =	$949.09		$1,016.2528	$1,016.27	$1,016.25	$1,016.20