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	$242.83	9.752%	$266.5108	$266.51	$266.50	$266.50
Purchase #2	$240.37	8.862%	$261.6716	$261.67	$261.65	$261.70
Purchase #3	$90.45	13.428%	$102.5956	$102.60	$102.60	$102.60
Purchase #4	$70.84	10.448%	$78.2414	$78.24	$78.25	$78.20
Purchase #5	$167.90	4.547%	$175.5344	$175.53	$175.55	$175.50
Purchase #6	$131.56	7.143%	$140.9573	$140.96	$140.95	$141.00
Purchase #7	$181.38	5.175%	$190.7664	$190.77	$190.75	$190.80
7 purchase totals =	$1,125.33		$1,216.2775	$1,216.28	$1,216.25	$1,216.30