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	$59.93	9.281%	$65.4921	$65.49	$65.50	$65.50
Purchase #2	$168.37	11.305%	$187.4042	$187.40	$187.40	$187.40
Purchase #3	$69.80	4.382%	$72.8586	$72.86	$72.85	$72.90
Purchase #4	$96.54	10.637%	$106.809	$106.81	$106.80	$106.80
Purchase #5	$116.34	4.435%	$121.4997	$121.50	$121.50	$121.50
Purchase #6	$162.34	4.480%	$169.6128	$169.61	$169.60	$169.60
Purchase #7	$16.55	13.635%	$18.8066	$18.81	$18.80	$18.80
7 purchase totals =	$689.87		$742.4830	$742.48	$742.45	$742.50