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	$60.81	11.543%	$67.8293	$67.83	$67.85	$67.80
Purchase #2	$172.69	13.632%	$196.2311	$196.23	$196.25	$196.20
Purchase #3	$13.81	12.324%	$15.5119	$15.51	$15.50	$15.50
Purchase #4	$59.46	6.521%	$63.3374	$63.34	$63.35	$63.30
Purchase #5	$213.96	5.293%	$225.2849	$225.28	$225.30	$225.30
Purchase #6	$178.45	11.135%	$198.3204	$198.32	$198.30	$198.30
Purchase #7	$12.43	9.550%	$13.6171	$13.62	$13.60	$13.60
7 purchase totals =	$711.61		$780.1321	$780.13	$780.15	$780.00