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	$212.90	13.452%	$241.5393	$241.54	$241.55	$241.50
Purchase #2	$148.39	8.681%	$161.2717	$161.27	$161.25	$161.30
Purchase #3	$145.90	12.513%	$164.1565	$164.16	$164.15	$164.20
Purchase #4	$179.94	11.439%	$200.5233	$200.52	$200.50	$200.50
Purchase #5	$231.86	7.727%	$249.7758	$249.78	$249.80	$249.80
Purchase #6	$130.90	4.298%	$136.5261	$136.53	$136.55	$136.50
Purchase #7	$46.35	11.717%	$51.7808	$51.78	$51.80	$51.80
7 purchase totals =	$1,096.24		$1,205.5735	$1,205.58	$1,205.60	$1,205.60