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	$192.84	3.623%	$199.8266	$199.83	$199.85	$199.80
Purchase #2	$40.93	7.665%	$44.0673	$44.07	$44.05	$44.10
Purchase #3	$45.96	5.603%	$48.5351	$48.54	$48.55	$48.50
Purchase #4	$66.32	7.729%	$71.4459	$71.45	$71.45	$71.40
Purchase #5	$13.96	11.813%	$15.6091	$15.61	$15.60	$15.60
Purchase #6	$172.91	7.361%	$185.6379	$185.64	$185.65	$185.60
Purchase #7	$178.66	11.832%	$199.7991	$199.80	$199.80	$199.80
7 purchase totals =	$711.58		$764.9210	$764.94	$764.95	$764.80