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	$143.58	5.409%	$151.3462	$151.35	$151.35	$151.30
Purchase #2	$37.85	11.572%	$42.23	$42.23	$42.25	$42.20
Purchase #3	$157.90	7.833%	$170.2683	$170.27	$170.25	$170.30
Purchase #4	$19.61	3.212%	$20.2399	$20.24	$20.25	$20.20
Purchase #5	$164.79	7.168%	$176.6021	$176.60	$176.60	$176.60
Purchase #6	$236.49	12.807%	$266.7773	$266.78	$266.80	$266.80
Purchase #7	$137.83	10.326%	$152.0623	$152.06	$152.05	$152.10
7 purchase totals =	$898.05		$979.5261	$979.53	$979.55	$979.50