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	$200.88	9.271%	$219.5036	$219.50	$219.50	$219.50
Purchase #2	$33.73	5.388%	$35.5474	$35.55	$35.55	$35.50
Purchase #3	$29.65	6.389%	$31.5443	$31.54	$31.55	$31.50
Purchase #4	$25.64	8.276%	$27.762	$27.76	$27.75	$27.80
Purchase #5	$173.56	6.723%	$185.2284	$185.23	$185.25	$185.20
Purchase #6	$207.96	8.262%	$225.1417	$225.14	$225.15	$225.10
Purchase #7	$145.65	8.802%	$158.4701	$158.47	$158.45	$158.50
7 purchase totals =	$817.07		$883.1975	$883.19	$883.20	$883.10