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	$214.32	10.467%	$236.7529	$236.75	$236.75	$236.80
Purchase #2	$78.74	5.675%	$83.2085	$83.21	$83.20	$83.20
Purchase #3	$100.52	4.834%	$105.3791	$105.38	$105.40	$105.40
Purchase #4	$140.78	10.384%	$155.3986	$155.40	$155.40	$155.40
Purchase #5	$161.76	4.360%	$168.8127	$168.81	$168.80	$168.80
Purchase #6	$9.49	10.626%	$10.4984	$10.50	$10.50	$10.50
Purchase #7	$170.97	8.422%	$185.3691	$185.37	$185.35	$185.40
7 purchase totals =	$876.58		$945.4193	$945.42	$945.40	$945.50