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	$187.54	6.434%	$199.6063	$199.61	$199.60	$199.60
Purchase #2	$85.93	5.818%	$90.9294	$90.93	$90.95	$90.90
Purchase #3	$155.89	10.660%	$172.5079	$172.51	$172.50	$172.50
Purchase #4	$150.96	4.289%	$157.4347	$157.43	$157.45	$157.40
Purchase #5	$88.39	8.816%	$96.1825	$96.18	$96.20	$96.20
Purchase #6	$145.52	11.385%	$162.0875	$162.09	$162.10	$162.10
Purchase #7	$138.44	10.641%	$153.1714	$153.17	$153.15	$153.20
7 purchase totals =	$952.67		$1,031.9197	$1,031.92	$1,031.95	$1,031.90