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	$133.33	8.643%	$144.8537	$144.85	$144.85	$144.90
Purchase #2	$101.64	3.575%	$105.2736	$105.27	$105.25	$105.30
Purchase #3	$105.33	8.616%	$114.4052	$114.41	$114.40	$114.40
Purchase #4	$212.67	11.247%	$236.589	$236.59	$236.60	$236.60
Purchase #5	$13.46	13.558%	$15.2849	$15.28	$15.30	$15.30
Purchase #6	$15.79	8.530%	$17.1369	$17.14	$17.15	$17.10
Purchase #7	$47.51	13.426%	$53.8887	$53.89	$53.90	$53.90
7 purchase totals =	$629.73		$687.4320	$687.43	$687.45	$687.50