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	$130.54	13.773%	$148.5193	$148.52	$148.50	$148.50
Purchase #2	$230.79	4.464%	$241.0925	$241.09	$241.10	$241.10
Purchase #3	$24.54	11.765%	$27.4271	$27.43	$27.45	$27.40
Purchase #4	$96.96	11.843%	$108.443	$108.44	$108.45	$108.40
Purchase #5	$84.72	3.752%	$87.8987	$87.90	$87.90	$87.90
Purchase #6	$241.87	13.307%	$274.0556	$274.06	$274.05	$274.10
Purchase #7	$142.56	7.278%	$152.9355	$152.94	$152.95	$152.90
7 purchase totals =	$951.98		$1,040.3717	$1,040.38	$1,040.40	$1,040.30