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	$142.94	7.638%	$153.8578	$153.86	$153.85	$153.90
Purchase #2	$237.90	4.683%	$249.0409	$249.04	$249.05	$249.00
Purchase #3	$34.45	9.385%	$37.6831	$37.68	$37.70	$37.70
Purchase #4	$247.41	3.413%	$255.8541	$255.85	$255.85	$255.90
Purchase #5	$48.79	9.150%	$53.2543	$53.25	$53.25	$53.30
Purchase #6	$171.89	11.737%	$192.0647	$192.06	$192.05	$192.10
Purchase #7	$95.90	6.683%	$102.309	$102.31	$102.30	$102.30
7 purchase totals =	$979.28		$1,044.0639	$1,044.05	$1,044.05	$1,044.20