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	$139.34	11.407%	$155.2345	$155.23	$155.25	$155.20
Purchase #2	$20.43	7.475%	$21.9571	$21.96	$21.95	$22.00
Purchase #3	$213.45	11.183%	$237.3201	$237.32	$237.30	$237.30
Purchase #4	$181.60	10.410%	$200.5046	$200.50	$200.50	$200.50
Purchase #5	$92.68	13.117%	$104.8368	$104.84	$104.85	$104.80
Purchase #6	$242.61	12.679%	$273.3705	$273.37	$273.35	$273.40
Purchase #7	$76.28	9.792%	$83.7493	$83.75	$83.75	$83.70
7 purchase totals =	$966.39		$1,076.9729	$1,076.97	$1,076.95	$1,076.90