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	$142.90	11.429%	$159.232	$159.23	$159.25	$159.20
Purchase #2	$84.98	9.172%	$92.7744	$92.77	$92.75	$92.80
Purchase #3	$47.40	7.812%	$51.1029	$51.10	$51.10	$51.10
Purchase #4	$237.85	6.791%	$254.0024	$254.00	$254.00	$254.00
Purchase #5	$233.93	10.773%	$259.1313	$259.13	$259.15	$259.10
Purchase #6	$94.68	6.779%	$101.0984	$101.10	$101.10	$101.10
Purchase #7	$90.56	9.381%	$99.0554	$99.06	$99.05	$99.10
7 purchase totals =	$932.30		$1,016.3968	$1,016.39	$1,016.40	$1,016.40