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	$68.46	13.737%	$77.8644	$77.86	$77.85	$77.90
Purchase #2	$182.73	4.648%	$191.2233	$191.22	$191.20	$191.20
Purchase #3	$242.25	5.501%	$255.5762	$255.58	$255.60	$255.60
Purchase #4	$12.38	5.775%	$13.0949	$13.09	$13.10	$13.10
Purchase #5	$163.43	3.117%	$168.5241	$168.52	$168.50	$168.50
Purchase #6	$144.50	5.357%	$152.2409	$152.24	$152.25	$152.20
Purchase #7	$85.53	4.151%	$89.0804	$89.08	$89.10	$89.10
7 purchase totals =	$899.28		$947.6042	$947.59	$947.60	$947.60