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	$127.76	11.859%	$142.9111	$142.91	$142.90	$142.90
Purchase #2	$100.89	3.631%	$104.5533	$104.55	$104.55	$104.60
Purchase #3	$238.47	7.130%	$255.4729	$255.47	$255.45	$255.50
Purchase #4	$237.75	5.452%	$250.7121	$250.71	$250.70	$250.70
Purchase #5	$138.96	11.818%	$155.3823	$155.38	$155.40	$155.40
Purchase #6	$66.41	9.626%	$72.8026	$72.80	$72.80	$72.80
Purchase #7	$103.55	10.156%	$114.0665	$114.07	$114.05	$114.10
7 purchase totals =	$1,013.79		$1,095.9008	$1,095.89	$1,095.85	$1,096.00