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	$105.93	12.369%	$119.0325	$119.03	$119.05	$119.00
Purchase #2	$75.72	12.393%	$85.104	$85.10	$85.10	$85.10
Purchase #3	$201.38	3.714%	$208.8593	$208.86	$208.85	$208.90
Purchase #4	$51.42	11.160%	$57.1585	$57.16	$57.15	$57.20
Purchase #5	$233.89	9.150%	$255.2909	$255.29	$255.30	$255.30
Purchase #6	$120.25	6.475%	$128.0362	$128.04	$128.05	$128.00
Purchase #7	$215.80	3.616%	$223.6033	$223.60	$223.60	$223.60
7 purchase totals =	$1,004.39		$1,077.0847	$1,077.08	$1,077.10	$1,077.10