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	$129.67	9.347%	$141.7903	$141.79	$141.80	$141.80
Purchase #2	$29.69	10.192%	$32.716	$32.72	$32.70	$32.70
Purchase #3	$40.44	5.645%	$42.7228	$42.72	$42.70	$42.70
Purchase #4	$198.54	8.417%	$215.2511	$215.25	$215.25	$215.30
Purchase #5	$147.39	11.757%	$164.7186	$164.72	$164.70	$164.70
Purchase #6	$23.25	9.536%	$25.4671	$25.47	$25.45	$25.50
Purchase #7	$115.97	3.115%	$119.5825	$119.58	$119.60	$119.60
7 purchase totals =	$684.95		$742.2484	$742.25	$742.20	$742.30