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	$167.65	11.105%	$186.2675	$186.27	$186.25	$186.30
Purchase #2	$241.83	3.203%	$249.5758	$249.58	$249.60	$249.60
Purchase #3	$52.54	13.249%	$59.501	$59.50	$59.50	$59.50
Purchase #4	$203.64	4.494%	$212.7916	$212.79	$212.80	$212.80
Purchase #5	$123.75	6.342%	$131.5982	$131.60	$131.60	$131.60
Purchase #6	$50.28	3.342%	$51.9604	$51.96	$51.95	$52.00
Purchase #7	$238.84	9.457%	$261.4271	$261.43	$261.45	$261.40
7 purchase totals =	$1,078.53		$1,153.1216	$1,153.13	$1,153.15	$1,153.20