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	$52.29	6.610%	$55.7464	$55.75	$55.75	$55.70
Purchase #2	$116.39	6.393%	$123.8308	$123.83	$123.85	$123.80
Purchase #3	$222.56	4.626%	$232.8556	$232.86	$232.85	$232.90
Purchase #4	$111.52	5.683%	$117.8577	$117.86	$117.85	$117.90
Purchase #5	$195.66	8.871%	$213.017	$213.02	$213.00	$213.00
Purchase #6	$78.94	9.286%	$86.2704	$86.27	$86.25	$86.30
Purchase #7	$135.42	5.471%	$142.8288	$142.83	$142.85	$142.80
7 purchase totals =	$912.78		$972.4067	$972.42	$972.40	$972.40