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	$147.80	8.425%	$160.2522	$160.25	$160.25	$160.30
Purchase #2	$139.63	10.382%	$154.1264	$154.13	$154.15	$154.10
Purchase #3	$193.32	3.193%	$199.4927	$199.49	$199.50	$199.50
Purchase #4	$122.74	4.131%	$127.8104	$127.81	$127.80	$127.80
Purchase #5	$83.47	13.491%	$94.7309	$94.73	$94.75	$94.70
Purchase #6	$77.81	4.661%	$81.4367	$81.44	$81.45	$81.40
Purchase #7	$180.76	9.691%	$198.2775	$198.28	$198.30	$198.30
7 purchase totals =	$945.53		$1,016.1268	$1,016.13	$1,016.20	$1,016.10