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	$154.31	12.449%	$173.5201	$173.52	$173.50	$173.50
Purchase #2	$150.31	10.615%	$166.2654	$166.27	$166.25	$166.30
Purchase #3	$110.87	3.675%	$114.9445	$114.94	$114.95	$114.90
Purchase #4	$111.39	9.330%	$121.7827	$121.78	$121.80	$121.80
Purchase #5	$98.89	13.856%	$112.5922	$112.59	$112.60	$112.60
Purchase #6	$213.91	5.414%	$225.4911	$225.49	$225.50	$225.50
Purchase #7	$29.84	13.706%	$33.9299	$33.93	$33.95	$33.90
7 purchase totals =	$869.52		$948.5259	$948.52	$948.55	$948.50