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	$21.93	7.376%	$23.5476	$23.55	$23.55	$23.50
Purchase #2	$103.64	7.607%	$111.5239	$111.52	$111.50	$111.50
Purchase #3	$95.47	5.589%	$100.8058	$100.81	$100.80	$100.80
Purchase #4	$133.97	8.187%	$144.9381	$144.94	$144.95	$144.90
Purchase #5	$171.93	11.122%	$191.0521	$191.05	$191.05	$191.10
Purchase #6	$37.82	9.539%	$41.4276	$41.43	$41.45	$41.40
Purchase #7	$142.50	8.277%	$154.2947	$154.29	$154.30	$154.30
7 purchase totals =	$707.26		$767.5898	$767.59	$767.60	$767.50