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	$177.46	11.829%	$198.4517	$198.45	$198.45	$198.50
Purchase #2	$75.99	3.456%	$78.6162	$78.62	$78.60	$78.60
Purchase #3	$150.97	6.585%	$160.9114	$160.91	$160.90	$160.90
Purchase #4	$80.39	3.719%	$83.3797	$83.38	$83.40	$83.40
Purchase #5	$225.39	7.246%	$241.7218	$241.72	$241.70	$241.70
Purchase #6	$150.89	12.523%	$169.786	$169.79	$169.80	$169.80
Purchase #7	$134.35	7.222%	$144.0528	$144.05	$144.05	$144.10
7 purchase totals =	$995.44		$1,076.9196	$1,076.92	$1,076.90	$1,077.00