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	$172.90	13.469%	$196.1879	$196.19	$196.20	$196.20
Purchase #2	$62.30	10.561%	$68.8795	$68.88	$68.90	$68.90
Purchase #3	$222.42	10.477%	$245.7229	$245.72	$245.70	$245.70
Purchase #4	$103.67	13.382%	$117.5431	$117.54	$117.55	$117.50
Purchase #5	$231.79	10.404%	$255.9054	$255.91	$255.90	$255.90
Purchase #6	$44.83	8.271%	$48.5379	$48.54	$48.55	$48.50
Purchase #7	$66.94	13.824%	$76.1938	$76.19	$76.20	$76.20
7 purchase totals =	$904.85		$1,008.9705	$1,008.97	$1,009.00	$1,008.90