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	$231.31	4.444%	$241.5894	$241.59	$241.60	$241.60
Purchase #2	$171.85	3.651%	$178.1242	$178.12	$178.10	$178.10
Purchase #3	$108.62	10.345%	$119.8567	$119.86	$119.85	$119.90
Purchase #4	$204.76	12.289%	$229.923	$229.92	$229.90	$229.90
Purchase #5	$38.79	13.524%	$44.036	$44.04	$44.05	$44.00
Purchase #6	$133.51	7.390%	$143.3764	$143.38	$143.40	$143.40
Purchase #7	$208.61	8.274%	$225.8704	$225.87	$225.85	$225.90
7 purchase totals =	$1,097.45		$1,182.7761	$1,182.78	$1,182.75	$1,182.80