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	$124.46	11.607%	$138.9061	$138.91	$138.90	$138.90
Purchase #2	$208.69	5.224%	$219.592	$219.59	$219.60	$219.60
Purchase #3	$150.43	11.105%	$167.1353	$167.14	$167.15	$167.10
Purchase #4	$167.78	6.493%	$178.674	$178.67	$178.65	$178.70
Purchase #5	$84.60	11.586%	$94.4018	$94.40	$94.40	$94.40
Purchase #6	$50.86	7.253%	$54.5489	$54.55	$54.55	$54.50
Purchase #7	$193.77	11.614%	$216.2744	$216.27	$216.25	$216.30
7 purchase totals =	$980.59		$1,069.5325	$1,069.53	$1,069.50	$1,069.50