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	$103.57	7.563%	$111.403	$111.40	$111.40	$111.40
Purchase #2	$42.63	4.203%	$44.4217	$44.42	$44.40	$44.40
Purchase #3	$67.54	4.821%	$70.7961	$70.80	$70.80	$70.80
Purchase #4	$248.94	13.180%	$281.7503	$281.75	$281.75	$281.80
Purchase #5	$140.93	13.562%	$160.0429	$160.04	$160.05	$160.00
Purchase #6	$12.59	6.105%	$13.3586	$13.36	$13.35	$13.40
Purchase #7	$160.73	8.543%	$174.4612	$174.46	$174.45	$174.50
7 purchase totals =	$776.93		$856.2338	$856.23	$856.20	$856.30