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	$164.94	9.450%	$180.5268	$180.53	$180.55	$180.50
Purchase #2	$54.31	3.575%	$56.2516	$56.25	$56.25	$56.30
Purchase #3	$143.81	4.499%	$150.28	$150.28	$150.30	$150.30
Purchase #4	$246.76	5.596%	$260.5687	$260.57	$260.55	$260.60
Purchase #5	$67.62	7.389%	$72.6164	$72.62	$72.60	$72.60
Purchase #6	$135.36	6.675%	$144.3953	$144.40	$144.40	$144.40
Purchase #7	$37.98	7.372%	$40.7799	$40.78	$40.80	$40.80
7 purchase totals =	$850.78		$905.4187	$905.43	$905.45	$905.50