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	$101.90	12.334%	$114.4683	$114.47	$114.45	$114.50
Purchase #2	$132.92	4.799%	$139.2988	$139.30	$139.30	$139.30
Purchase #3	$82.68	8.268%	$89.516	$89.52	$89.50	$89.50
Purchase #4	$139.90	13.110%	$158.2409	$158.24	$158.25	$158.20
Purchase #5	$227.37	4.179%	$236.8718	$236.87	$236.85	$236.90
Purchase #6	$164.77	9.392%	$180.2452	$180.25	$180.25	$180.20
Purchase #7	$139.38	13.685%	$158.4542	$158.45	$158.45	$158.50
7 purchase totals =	$988.92		$1,077.0952	$1,077.10	$1,077.05	$1,077.10