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	$153.64	11.590%	$171.4469	$171.45	$171.45	$171.40
Purchase #2	$100.46	12.298%	$112.8146	$112.81	$112.80	$112.80
Purchase #3	$144.59	4.828%	$151.5708	$151.57	$151.55	$151.60
Purchase #4	$136.40	13.485%	$154.7935	$154.79	$154.80	$154.80
Purchase #5	$95.71	4.612%	$100.1241	$100.12	$100.10	$100.10
Purchase #6	$23.56	3.807%	$24.4569	$24.46	$24.45	$24.50
Purchase #7	$56.88	11.285%	$63.2989	$63.30	$63.30	$63.30
7 purchase totals =	$711.24		$778.5057	$778.50	$778.45	$778.50