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	$125.45	12.105%	$140.6357	$140.64	$140.65	$140.60
Purchase #2	$172.96	3.583%	$179.1572	$179.16	$179.15	$179.20
Purchase #3	$141.71	8.849%	$154.2499	$154.25	$154.25	$154.20
Purchase #4	$198.55	6.213%	$210.8859	$210.89	$210.90	$210.90
Purchase #5	$57.94	12.626%	$65.2555	$65.26	$65.25	$65.30
Purchase #6	$143.39	5.333%	$151.037	$151.04	$151.05	$151.00
Purchase #7	$102.85	9.205%	$112.3173	$112.32	$112.30	$112.30
7 purchase totals =	$942.85		$1,013.5385	$1,013.56	$1,013.55	$1,013.50