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	$131.82	9.356%	$144.1531	$144.15	$144.15	$144.20
Purchase #2	$196.43	8.804%	$213.7237	$213.72	$213.70	$213.70
Purchase #3	$112.39	7.609%	$120.9418	$120.94	$120.95	$120.90
Purchase #4	$62.30	4.407%	$65.0456	$65.05	$65.05	$65.00
Purchase #5	$209.81	5.149%	$220.6131	$220.61	$220.60	$220.60
Purchase #6	$96.31	10.680%	$106.5959	$106.60	$106.60	$106.60
Purchase #7	$81.98	11.525%	$91.4282	$91.43	$91.45	$91.40
7 purchase totals =	$891.04		$962.5014	$962.50	$962.50	$962.40