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	$126.32	12.482%	$142.0873	$142.09	$142.10	$142.10
Purchase #2	$212.34	7.699%	$228.6881	$228.69	$228.70	$228.70
Purchase #3	$68.97	12.274%	$77.4354	$77.44	$77.45	$77.40
Purchase #4	$185.77	7.113%	$198.9838	$198.98	$199.00	$199.00
Purchase #5	$233.94	12.314%	$262.7474	$262.75	$262.75	$262.70
Purchase #6	$113.93	12.264%	$127.9024	$127.90	$127.90	$127.90
Purchase #7	$70.75	10.683%	$78.3082	$78.31	$78.30	$78.30
7 purchase totals =	$1,012.02		$1,116.1526	$1,116.16	$1,116.20	$1,116.10