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	$95.75	12.287%	$107.5148	$107.51	$107.50	$107.50
Purchase #2	$204.55	3.457%	$211.6213	$211.62	$211.60	$211.60
Purchase #3	$86.43	4.590%	$90.3971	$90.40	$90.40	$90.40
Purchase #4	$113.74	8.538%	$123.4511	$123.45	$123.45	$123.50
Purchase #5	$52.89	5.219%	$55.6503	$55.65	$55.65	$55.70
Purchase #6	$159.90	5.401%	$168.5362	$168.54	$168.55	$168.50
Purchase #7	$166.26	10.108%	$183.0656	$183.07	$183.05	$183.10
7 purchase totals =	$879.52		$940.2364	$940.24	$940.20	$940.30