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	$143.53	4.224%	$149.5927	$149.59	$149.60	$149.60
Purchase #2	$144.61	3.726%	$149.9982	$150.00	$150.00	$150.00
Purchase #3	$72.39	8.118%	$78.2666	$78.27	$78.25	$78.30
Purchase #4	$81.51	4.811%	$85.4314	$85.43	$85.45	$85.40
Purchase #5	$104.52	4.225%	$108.936	$108.94	$108.95	$108.90
Purchase #6	$104.68	12.851%	$118.1324	$118.13	$118.15	$118.10
Purchase #7	$69.46	9.565%	$76.1038	$76.10	$76.10	$76.10
7 purchase totals =	$720.70		$766.4611	$766.46	$766.50	$766.40