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	$133.54	7.428%	$143.4594	$143.46	$143.45	$143.50
Purchase #2	$49.28	13.245%	$55.8071	$55.81	$55.80	$55.80
Purchase #3	$244.73	6.112%	$259.6879	$259.69	$259.70	$259.70
Purchase #4	$131.98	9.836%	$144.9616	$144.96	$144.95	$145.00
Purchase #5	$103.78	12.590%	$116.8459	$116.85	$116.85	$116.80
Purchase #6	$174.45	13.730%	$198.402	$198.40	$198.40	$198.40
Purchase #7	$204.80	5.276%	$215.6052	$215.61	$215.60	$215.60
7 purchase totals =	$1,042.56		$1,134.7691	$1,134.78	$1,134.75	$1,134.80