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	$158.85	13.615%	$180.4774	$180.48	$180.50	$180.50
Purchase #2	$56.27	4.674%	$58.9001	$58.90	$58.90	$58.90
Purchase #3	$168.45	10.264%	$185.7397	$185.74	$185.75	$185.70
Purchase #4	$30.25	8.487%	$32.8173	$32.82	$32.80	$32.80
Purchase #5	$153.67	7.724%	$165.5395	$165.54	$165.55	$165.50
Purchase #6	$113.55	12.456%	$127.6938	$127.69	$127.70	$127.70
Purchase #7	$113.72	10.857%	$126.0666	$126.07	$126.05	$126.10
7 purchase totals =	$794.76		$877.2344	$877.24	$877.25	$877.20