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	$211.63	13.703%	$240.6297	$240.63	$240.65	$240.60
Purchase #2	$166.43	3.816%	$172.781	$172.78	$172.80	$172.80
Purchase #3	$63.57	10.265%	$70.0955	$70.10	$70.10	$70.10
Purchase #4	$51.29	11.509%	$57.193	$57.19	$57.20	$57.20
Purchase #5	$179.47	10.440%	$198.2067	$198.21	$198.20	$198.20
Purchase #6	$80.98	5.387%	$85.3424	$85.34	$85.35	$85.30
Purchase #7	$173.42	10.222%	$191.147	$191.15	$191.15	$191.10
7 purchase totals =	$926.79		$1,015.3953	$1,015.40	$1,015.45	$1,015.30