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	$62.89	13.523%	$71.3946	$71.39	$71.40	$71.40
Purchase #2	$239.32	6.854%	$255.723	$255.72	$255.70	$255.70
Purchase #3	$27.87	3.143%	$28.746	$28.75	$28.75	$28.70
Purchase #4	$133.48	13.221%	$151.1274	$151.13	$151.15	$151.10
Purchase #5	$80.89	11.584%	$90.2603	$90.26	$90.25	$90.30
Purchase #6	$80.54	7.115%	$86.2704	$86.27	$86.25	$86.30
Purchase #7	$86.60	9.663%	$94.9682	$94.97	$94.95	$95.00
7 purchase totals =	$711.59		$778.4899	$778.49	$778.45	$778.50