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	$143.94	11.478%	$160.4614	$160.46	$160.45	$160.50
Purchase #2	$33.43	12.166%	$37.4971	$37.50	$37.50	$37.50
Purchase #3	$70.76	9.724%	$77.6407	$77.64	$77.65	$77.60
Purchase #4	$38.82	7.555%	$41.7529	$41.75	$41.75	$41.80
Purchase #5	$229.85	11.264%	$255.7403	$255.74	$255.75	$255.70
Purchase #6	$247.28	6.700%	$263.8478	$263.85	$263.85	$263.80
Purchase #7	$119.69	5.665%	$126.4704	$126.47	$126.45	$126.50
7 purchase totals =	$883.77		$963.4106	$963.41	$963.40	$963.40