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	$77.68	3.862%	$80.68	$80.68	$80.70	$80.70
Purchase #2	$107.27	4.195%	$111.77	$111.77	$111.75	$111.80
Purchase #3	$185.32	4.366%	$193.4111	$193.41	$193.40	$193.40
Purchase #4	$26.40	4.307%	$27.537	$27.54	$27.55	$27.50
Purchase #5	$132.71	8.854%	$144.4601	$144.46	$144.45	$144.50
Purchase #6	$217.72	13.400%	$246.8945	$246.89	$246.90	$246.90
Purchase #7	$222.82	9.541%	$244.0793	$244.08	$244.10	$244.10
7 purchase totals =	$969.92		$1,048.8320	$1,048.83	$1,048.85	$1,048.90