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	$164.38	11.364%	$183.0601	$183.06	$183.05	$183.10
Purchase #2	$235.96	12.150%	$264.6291	$264.63	$264.65	$264.60
Purchase #3	$16.88	9.665%	$18.5115	$18.51	$18.50	$18.50
Purchase #4	$111.91	10.410%	$123.5598	$123.56	$123.55	$123.60
Purchase #5	$138.88	3.367%	$143.5561	$143.56	$143.55	$143.60
Purchase #6	$7.70	7.775%	$8.2987	$8.30	$8.30	$8.30
Purchase #7	$126.67	13.564%	$143.8515	$143.85	$143.85	$143.90
7 purchase totals =	$802.38		$885.4668	$885.47	$885.45	$885.60