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	$151.84	9.471%	$166.2208	$166.22	$166.20	$166.20
Purchase #2	$105.76	7.559%	$113.7544	$113.75	$113.75	$113.80
Purchase #3	$157.78	7.467%	$169.5614	$169.56	$169.55	$169.60
Purchase #4	$97.34	5.108%	$102.3121	$102.31	$102.30	$102.30
Purchase #5	$40.77	5.117%	$42.8562	$42.86	$42.85	$42.90
Purchase #6	$74.72	5.493%	$78.8244	$78.82	$78.80	$78.80
Purchase #7	$21.29	10.855%	$23.601	$23.60	$23.60	$23.60
7 purchase totals =	$649.50		$697.1303	$697.12	$697.05	$697.20