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	$95.55	10.706%	$105.7796	$105.78	$105.80	$105.80
Purchase #2	$152.71	3.626%	$158.2473	$158.25	$158.25	$158.20
Purchase #3	$243.57	9.147%	$265.8493	$265.85	$265.85	$265.80
Purchase #4	$212.32	5.346%	$223.6706	$223.67	$223.65	$223.70
Purchase #5	$217.93	3.382%	$225.3004	$225.30	$225.30	$225.30
Purchase #6	$42.34	9.273%	$46.2662	$46.27	$46.25	$46.30
Purchase #7	$127.44	10.484%	$140.8008	$140.80	$140.80	$140.80
7 purchase totals =	$1,091.86		$1,165.9142	$1,165.92	$1,165.90	$1,165.90