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	$142.86	9.730%	$156.7603	$156.76	$156.75	$156.80
Purchase #2	$232.64	12.449%	$261.6014	$261.60	$261.60	$261.60
Purchase #3	$173.52	11.135%	$192.8415	$192.84	$192.85	$192.80
Purchase #4	$45.74	12.253%	$51.3445	$51.34	$51.35	$51.30
Purchase #5	$242.25	5.573%	$255.7506	$255.75	$255.75	$255.80
Purchase #6	$106.39	13.509%	$120.7622	$120.76	$120.75	$120.80
Purchase #7	$68.92	4.808%	$72.2337	$72.23	$72.25	$72.20
7 purchase totals =	$1,012.32		$1,111.2942	$1,111.28	$1,111.30	$1,111.30