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	$166.26	10.421%	$183.586	$183.59	$183.60	$183.60
Purchase #2	$88.75	6.453%	$94.477	$94.48	$94.50	$94.50
Purchase #3	$195.51	6.464%	$208.1478	$208.15	$208.15	$208.10
Purchase #4	$246.80	13.693%	$280.5943	$280.59	$280.60	$280.60
Purchase #5	$90.59	4.680%	$94.8296	$94.83	$94.85	$94.80
Purchase #6	$106.51	8.749%	$115.8286	$115.83	$115.85	$115.80
Purchase #7	$41.94	7.419%	$45.0515	$45.05	$45.05	$45.10
7 purchase totals =	$936.36		$1,022.5148	$1,022.52	$1,022.60	$1,022.50