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	$175.97	8.238%	$190.4664	$190.47	$190.45	$190.50
Purchase #2	$134.29	6.385%	$142.8644	$142.86	$142.85	$142.90
Purchase #3	$104.84	9.155%	$114.4381	$114.44	$114.45	$114.40
Purchase #4	$182.64	9.830%	$200.5935	$200.59	$200.60	$200.60
Purchase #5	$41.79	7.440%	$44.8992	$44.90	$44.90	$44.90
Purchase #6	$129.64	4.333%	$135.2573	$135.26	$135.25	$135.30
Purchase #7	$241.43	3.308%	$249.4165	$249.42	$249.40	$249.40
7 purchase totals =	$1,010.60		$1,077.9354	$1,077.94	$1,077.90	$1,078.00