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	$137.68	4.872%	$144.3878	$144.39	$144.40	$144.40
Purchase #2	$166.27	6.129%	$176.4607	$176.46	$176.45	$176.50
Purchase #3	$101.68	9.854%	$111.6995	$111.70	$111.70	$111.70
Purchase #4	$217.60	7.371%	$233.6393	$233.64	$233.65	$233.60
Purchase #5	$87.96	5.582%	$92.8699	$92.87	$92.85	$92.90
Purchase #6	$215.57	8.288%	$233.4364	$233.44	$233.45	$233.40
Purchase #7	$149.72	5.228%	$157.5474	$157.55	$157.55	$157.50
7 purchase totals =	$1,076.48		$1,150.0410	$1,150.05	$1,150.05	$1,150.00