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	$153.40	9.685%	$168.2568	$168.26	$168.25	$168.30
Purchase #2	$220.56	9.401%	$241.2948	$241.29	$241.30	$241.30
Purchase #3	$188.49	13.422%	$213.7891	$213.79	$213.80	$213.80
Purchase #4	$46.38	13.121%	$52.4655	$52.47	$52.45	$52.50
Purchase #5	$176.56	5.869%	$186.9223	$186.92	$186.90	$186.90
Purchase #6	$114.93	13.317%	$130.2352	$130.24	$130.25	$130.20
Purchase #7	$51.31	8.349%	$55.5939	$55.59	$55.60	$55.60
7 purchase totals =	$951.63		$1,048.5576	$1,048.56	$1,048.55	$1,048.60