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	$105.47	5.487%	$111.2571	$111.26	$111.25	$111.30
Purchase #2	$88.34	4.659%	$92.4558	$92.46	$92.45	$92.50
Purchase #3	$9.52	5.602%	$10.0533	$10.05	$10.05	$10.10
Purchase #4	$80.55	12.430%	$90.5624	$90.56	$90.55	$90.60
Purchase #5	$213.72	8.542%	$231.976	$231.98	$232.00	$232.00
Purchase #6	$248.94	13.660%	$282.9452	$282.95	$282.95	$282.90
Purchase #7	$80.81	12.637%	$91.022	$91.02	$91.00	$91.00
7 purchase totals =	$827.35		$910.2718	$910.28	$910.25	$910.40