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	$99.80	12.472%	$112.2471	$112.25	$112.25	$112.20
Purchase #2	$15.66	12.427%	$17.6061	$17.61	$17.60	$17.60
Purchase #3	$52.92	6.156%	$56.1778	$56.18	$56.20	$56.20
Purchase #4	$247.25	13.645%	$280.9873	$280.99	$281.00	$281.00
Purchase #5	$139.34	11.537%	$155.4157	$155.42	$155.40	$155.40
Purchase #6	$45.60	12.775%	$51.4254	$51.43	$51.45	$51.40
Purchase #7	$104.86	6.650%	$111.8332	$111.83	$111.85	$111.80
7 purchase totals =	$705.43		$785.6926	$785.71	$785.75	$785.60