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	$51.79	9.102%	$56.5039	$56.50	$56.50	$56.50
Purchase #2	$215.95	11.758%	$241.3414	$241.34	$241.35	$241.30
Purchase #3	$168.31	11.373%	$187.4519	$187.45	$187.45	$187.50
Purchase #4	$55.65	10.476%	$61.4799	$61.48	$61.50	$61.50
Purchase #5	$160.38	12.341%	$180.1725	$180.17	$180.15	$180.20
Purchase #6	$179.28	8.440%	$194.4112	$194.41	$194.40	$194.40
Purchase #7	$138.65	3.176%	$143.0535	$143.05	$143.05	$143.10
7 purchase totals =	$970.01		$1,064.4143	$1,064.40	$1,064.40	$1,064.50