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	$141.65	4.659%	$148.2495	$148.25	$148.25	$148.20
Purchase #2	$107.56	8.191%	$116.3702	$116.37	$116.35	$116.40
Purchase #3	$111.50	11.808%	$124.6659	$124.67	$124.65	$124.70
Purchase #4	$147.45	11.565%	$164.5026	$164.50	$164.50	$164.50
Purchase #5	$73.77	6.377%	$78.4743	$78.47	$78.45	$78.50
Purchase #6	$137.70	3.121%	$141.9976	$142.00	$142.00	$142.00
Purchase #7	$121.60	12.713%	$137.059	$137.06	$137.05	$137.10
7 purchase totals =	$841.23		$911.3191	$911.32	$911.25	$911.40