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	$165.59	9.160%	$180.758	$180.76	$180.75	$180.80
Purchase #2	$33.32	12.349%	$37.4347	$37.43	$37.45	$37.40
Purchase #3	$151.96	8.310%	$164.5879	$164.59	$164.60	$164.60
Purchase #4	$247.75	5.316%	$260.9204	$260.92	$260.90	$260.90
Purchase #5	$38.97	8.407%	$42.2462	$42.25	$42.25	$42.20
Purchase #6	$52.37	8.451%	$56.7958	$56.80	$56.80	$56.80
Purchase #7	$241.94	12.772%	$272.8406	$272.84	$272.85	$272.80
7 purchase totals =	$931.90		$1,015.5836	$1,015.59	$1,015.60	$1,015.50