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	$168.45	13.416%	$191.0493	$191.05	$191.05	$191.00
Purchase #2	$72.29	8.602%	$78.5084	$78.51	$78.50	$78.50
Purchase #3	$90.38	6.156%	$95.9438	$95.94	$95.95	$95.90
Purchase #4	$139.87	12.391%	$157.2013	$157.20	$157.20	$157.20
Purchase #5	$22.76	13.730%	$25.8849	$25.88	$25.90	$25.90
Purchase #6	$167.69	7.771%	$180.7212	$180.72	$180.70	$180.70
Purchase #7	$180.78	9.699%	$198.3139	$198.31	$198.30	$198.30
7 purchase totals =	$842.22		$927.6228	$927.61	$927.60	$927.50