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	$22.45	10.589%	$24.8272	$24.83	$24.85	$24.80
Purchase #2	$157.77	8.817%	$171.6806	$171.68	$171.70	$171.70
Purchase #3	$186.60	4.674%	$195.3217	$195.32	$195.30	$195.30
Purchase #4	$85.33	6.169%	$90.594	$90.59	$90.60	$90.60
Purchase #5	$129.55	10.536%	$143.1994	$143.20	$143.20	$143.20
Purchase #6	$142.48	5.283%	$150.0072	$150.01	$150.00	$150.00
Purchase #7	$131.95	12.610%	$148.5889	$148.59	$148.60	$148.60
7 purchase totals =	$856.13		$924.2190	$924.22	$924.25	$924.20