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	$238.25	9.371%	$260.5764	$260.58	$260.60	$260.60
Purchase #2	$183.81	4.239%	$191.6017	$191.60	$191.60	$191.60
Purchase #3	$178.25	7.650%	$191.8861	$191.89	$191.90	$191.90
Purchase #4	$62.32	7.658%	$67.0925	$67.09	$67.10	$67.10
Purchase #5	$43.87	5.245%	$46.171	$46.17	$46.15	$46.20
Purchase #6	$215.30	12.422%	$242.0446	$242.04	$242.05	$242.00
Purchase #7	$37.73	13.629%	$42.8722	$42.87	$42.85	$42.90
7 purchase totals =	$959.53		$1,042.2445	$1,042.24	$1,042.25	$1,042.30