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	$216.78	9.318%	$236.9796	$236.98	$237.00	$237.00
Purchase #2	$208.40	11.809%	$233.01	$233.01	$233.00	$233.00
Purchase #3	$172.76	4.844%	$181.1285	$181.13	$181.15	$181.10
Purchase #4	$47.58	5.206%	$50.057	$50.06	$50.05	$50.10
Purchase #5	$187.64	6.788%	$200.377	$200.38	$200.40	$200.40
Purchase #6	$224.27	13.271%	$254.0329	$254.03	$254.05	$254.00
Purchase #7	$169.50	12.103%	$190.0146	$190.01	$190.00	$190.00
7 purchase totals =	$1,226.93		$1,345.5996	$1,345.60	$1,345.65	$1,345.60