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	$108.30	6.732%	$115.5908	$115.59	$115.60	$115.60
Purchase #2	$246.60	13.208%	$279.1709	$279.17	$279.15	$279.20
Purchase #3	$214.85	10.584%	$237.5897	$237.59	$237.60	$237.60
Purchase #4	$245.59	5.384%	$258.8126	$258.81	$258.80	$258.80
Purchase #5	$178.66	7.364%	$191.8165	$191.82	$191.80	$191.80
Purchase #6	$168.47	7.567%	$181.2181	$181.22	$181.20	$181.20
Purchase #7	$161.38	7.114%	$172.8606	$172.86	$172.85	$172.90
7 purchase totals =	$1,323.85		$1,437.0592	$1,437.06	$1,437.00	$1,437.10