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	$90.51	5.412%	$95.4084	$95.41	$95.40	$95.40
Purchase #2	$14.56	4.208%	$15.1727	$15.17	$15.15	$15.20
Purchase #3	$97.30	5.712%	$102.8578	$102.86	$102.85	$102.90
Purchase #4	$78.95	7.856%	$85.1523	$85.15	$85.15	$85.20
Purchase #5	$49.32	8.259%	$53.3933	$53.39	$53.40	$53.40
Purchase #6	$86.68	6.658%	$92.4512	$92.45	$92.45	$92.50
Purchase #7	$222.52	8.455%	$241.3341	$241.33	$241.35	$241.30
7 purchase totals =	$639.84		$685.7698	$685.76	$685.75	$685.90