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	$83.84	13.153%	$94.8675	$94.87	$94.85	$94.90
Purchase #2	$241.86	5.608%	$255.4235	$255.42	$255.40	$255.40
Purchase #3	$142.87	8.218%	$154.6111	$154.61	$154.60	$154.60
Purchase #4	$98.34	13.545%	$111.6602	$111.66	$111.65	$111.70
Purchase #5	$29.95	8.417%	$32.4709	$32.47	$32.45	$32.50
Purchase #6	$157.66	12.417%	$177.2366	$177.24	$177.25	$177.20
Purchase #7	$89.91	7.184%	$96.3691	$96.37	$96.35	$96.40
7 purchase totals =	$844.43		$922.6389	$922.64	$922.55	$922.70