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	$160.72	9.853%	$176.5557	$176.56	$176.55	$176.60
Purchase #2	$151.72	4.449%	$158.47	$158.47	$158.45	$158.50
Purchase #3	$129.62	11.172%	$144.1011	$144.10	$144.10	$144.10
Purchase #4	$185.56	7.799%	$200.0318	$200.03	$200.05	$200.00
Purchase #5	$56.46	13.118%	$63.8664	$63.87	$63.85	$63.90
Purchase #6	$32.69	8.102%	$35.3385	$35.34	$35.35	$35.30
Purchase #7	$164.69	3.297%	$170.1198	$170.12	$170.10	$170.10
7 purchase totals =	$881.46		$948.4833	$948.49	$948.45	$948.50