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	$209.56	11.779%	$234.2441	$234.24	$234.25	$234.20
Purchase #2	$141.85	6.105%	$150.5099	$150.51	$150.50	$150.50
Purchase #3	$180.30	5.815%	$190.7844	$190.78	$190.80	$190.80
Purchase #4	$206.50	4.411%	$215.6087	$215.61	$215.60	$215.60
Purchase #5	$167.93	8.656%	$182.466	$182.47	$182.45	$182.50
Purchase #6	$206.73	10.623%	$228.6909	$228.69	$228.70	$228.70
Purchase #7	$175.31	5.357%	$184.7014	$184.70	$184.70	$184.70
7 purchase totals =	$1,288.18		$1,387.0054	$1,387.00	$1,387.00	$1,387.00